Patent Publication Number: US-11035692-B2

Title: Technologies for pedometric sensing in footwear

Description:
BACKGROUND 
     It is suggested that every person walk ten thousand steps every day for healthy living and maintaining proper body weight. To assist people in tracking their footsteps, commercial pedometers have been introduced to the marketplace. Generally, these pedometers are worn on the waist and use magnetic pendulums to sense the wearer&#39;s feet impacting the ground and/or the movement of the wearer&#39;s hips. These forces cause the magnetic pendulums to open and close an electrical circuit to register the wearer&#39;s steps. However, such devices are prone to false positives on events when the wearer shakes his body or moves his feet while sitting. Additionally, some pedometers require a calibration process in order to identify an ideal position on the wearer&#39;s body to detect footsteps and to differentiate a signal associated with a footstep from other occurrences. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The concepts described herein are illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. Where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. 
         FIG. 1  is a simplified block diagram of at least one embodiment of a system for tracking footsteps of a user; 
         FIG. 2  is a simplified block diagram of at least one embodiment of a footwear compute device of the system of  FIG. 1 ; 
         FIG. 3  is a simplified block diagram of at least one embodiment of a step tracker compute device of the system of  FIG. 1 ; 
         FIG. 4  is a simplified block diagram of at least one embodiment of an environment that may be established by a footwear compute device of  FIGS. 1 and 2 ; 
         FIG. 5  is a simplified block diagram of at least one embodiment of an environment that may be established by a step tracker compute device of  FIGS. 1 and 3 ; 
         FIG. 6  is a simplified flow diagram of at least one embodiment of a method for monitoring foot movement that may be performed by the footwear compute device of  FIGS. 1 and 2 ; 
         FIGS. 7-9  are a simplified flow diagram of at least one embodiment of a method for tracking steps of a user that may be performed by the step tracker compute device of  FIGS. 1 and 3 ; 
         FIG. 10  is a simplified diagram of at least one embodiment of a shoe that includes the footwear compute device of  FIGS. 1 and 2 ; 
         FIG. 11  is a plot of acceleration data over time that may be analyzed by the step tracker compute device of  FIGS. 1 and 3 ; 
         FIG. 12  is a plot of at least one embodiment of energy contour data over time that may be analyzed by the step tracker compute device of  FIGS. 1 and 3 ; 
         FIG. 13  is a plot of at least one embodiment of the energy contour data over time after a band pass filter has been applied by the step tracker compute device of  FIGS. 1 and 3 ; 
         FIG. 14  is a plot of at least one embodiment of the energy contour data over time after negative masking has been applied by the step tracker compute device of  FIGS. 1 and 3 ; and 
         FIG. 15  is a plot of at least one embodiment of the energy contour data after the band pass filter and negative masking have been applied and the step tracker compute device of  FIGS. 1 and 3  has determined dynamic energy thresholds to detect steps. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described herein in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims. 
     References in the specification to “one embodiment,” “an embodiment,” “an illustrative embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may or may not necessarily include that particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. Additionally, it should be appreciated that items included in a list in the form of “at least one A, B, and C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). Similarly, items listed in the form of “at least one of A, B, or C” can mean (A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C). 
     The disclosed embodiments may be implemented, in some cases, in hardware, firmware, software, or any combination thereof. The disclosed embodiments may also be implemented as instructions carried by or stored on a transitory or non-transitory machine-readable (e.g., computer-readable) storage medium, which may be read and executed by one or more processors. A machine-readable storage medium may be embodied as any storage device, mechanism, or other physical structure for storing or transmitting information in a form readable by a machine (e.g., a volatile or non-volatile memory, a media disc, or other media device). 
     In the drawings, some structural or method features may be shown in specific arrangements and/or orderings. However, it should be appreciated that such specific arrangements and/or orderings may not be required. Rather, in some embodiments, such features may be arranged in a different manner and/or order than shown in the illustrative figures. Additionally, the inclusion of a structural or method feature in a particular figure is not meant to imply that such feature is required in all embodiments and, in some embodiments, may not be included or may be combined with other features. 
     Referring now to  FIG. 1 , in an illustrative embodiment, a system  100  for tracking footsteps of a user includes a set of footwear compute devices  110  in communication with a step tracker compute device  120 , which is in communication with a server compute device  130  through a network  140 . In the illustrative embodiment, the set of footwear compute devices  110  includes a footwear compute device  112  incorporated into footwear (e.g., a shoe) of a user and another footwear compute device  114  incorporated into the footwear (e.g., the other shoe) of the user. In operation, the illustrative footwear compute device  110  senses acceleration of the user&#39;s foot in three dimensions and provides acceleration data to the step tracker compute device  120 . Further, in the illustrative embodiment, the footwear compute device  110  includes a power conversion device to obtain power in one form, such as from impacts of the shoe against the ground or from sunlight, and provides the power in a second form (e.g., electricity) to the components of the footwear compute device  110 . In the illustrative embodiment, the step tracker compute device  120 , in operation, analyzes the acceleration data to dynamically determine energy thresholds that are indicative of steps of the user as the user&#39;s pace and gait change in response to changing environments. By dynamically determining the energy thresholds, the step tracker compute device  120  removes the need for the user of the step tracker compute device  120  to perform a calibration process with the step tracker compute device  120  before walking. Additionally, in the illustrative embodiment, the step tracker compute device  120 , in operation, transmits data indicative of the detected steps to the server compute device  130  for storage and/or analysis. 
     Referring now to  FIG. 2 , each footwear compute device  110  may be embodied as any type of compute device capable of performing the functions described herein. In the illustrative embodiment, the footwear compute device  110  is incorporated into an article of footwear, such as a shoe, boot, or sandal. The footwear compute device  110  may be distributed across different portions of the footwear, including portions of the sole, sides, or top of the footwear. As shown in  FIG. 2 , the illustrative footwear compute device  110  includes a controller  202 , a main memory  204 , an input/output subsystem  206 , an acceleration sensor  208 , one or more power conversion devices  210 , and a communication subsystem  218 . Of course, the footwear compute device  110  may include other or additional components, such as those commonly found in a computer (e.g., data storage, etc.), in other embodiments. Additionally, in some embodiments, one or more of the illustrative components may be incorporated in, or otherwise from a portion of, another component. For example, the memory  204 , or portions thereof, may be incorporated in the controller  202  in some embodiments. 
     The controller  202  may be embodied as any type of processing device capable of performing the functions described herein. For example, the controller may be embodied as a microcontroller, single or multi-core processor(s) having one or more processor cores, a digital signal processor, or other processor or processing/controlling circuit. Similarly, the main memory  204  may be embodied as any type of volatile or non-volatile memory or data storage capable of performing the functions described herein. In operation, the main memory  204  may store various data and software used during operation of the footwear compute device  110  such as acceleration data from the acceleration sensor  208 , operating systems, applications, programs, libraries, and drivers. The main memory  204  is communicatively coupled to the controller  202  via the I/O subsystem  206 . Of course, in other embodiments (e.g., those in which the controller  202  includes a memory controller), the main memory  204  may be directly communicatively coupled to the controller  202 . 
     The I/O subsystem  206  may be embodied as circuitry and/or components to facilitate input/output operations with the controller  202 , the main memory  204 , and other components of the footwear compute device  110 . For example, the I/O subsystem  206  may be embodied as, or otherwise include, memory controller hubs, input/output control hubs, firmware devices, communication links (i.e., point-to-point links, bus links, wires, cables, light guides, printed circuit board traces, etc.) and/or other components and subsystems to facilitate the input/output operations. In some embodiments, the I/O subsystem  206  may form a portion of a system-on-a-chip (SoC) and be incorporated, along with the controller  202 , the memory  204 , and other components of the footwear compute device  110 , on a single integrated circuit chip. 
     The acceleration sensor  208  may be embodied as any type of device capable of detecting and measuring acceleration, such as a micro electro-mechanical system (MEMS) including one or more cantilever beams and proof masses, one or more capacitive accelerometers, one or more piezoelectric accelerometers, or other devices. In the illustrative embodiment, the acceleration sensor  208  is capable of detecting and measuring acceleration in three spatial dimensions. The acceleration sensor  208  may be configured to provide acceleration data indicative of sensed acceleration in three dimensions to the controller  202  in a digital format or an analog format (e.g., a voltage level associated with each dimension) on a continual basis (i.e., at a repeating time interval). 
     The one or more power conversion devices  210  may be embodied as any devices capable of obtaining power in one form and converting the power to another form, for use by the footwear compute device  110 . As such, the power conversion devices  210  may include a piezoelectric device  212 , a photovoltaic device  214  (i.e., one or more solar cells), or other power conversion devices  216  capable of performing the functions described herein. The piezoelectric device  212  is any device capable of utilizing the piezoelectric effect to generate an electric charge in response to applied mechanical stress. As such, the piezoelectric device  212  may include any one or more materials, such as naturally occurring crystals (e.g., quartz) or synthetic materials (e.g., langasite) to produce an electric charge in response to mechanical stress. As described in more detail herein, the piezoelectric device  212  may be incorporated into a sole of a shoe or other article of footwear to convert the mechanical stress of a user&#39;s foot impacting the ground to electricity for use by the footwear compute device  110 . The photovoltaic device  214  may be embodied as any device capable of utilizing the photoelectric effect to produce electrical energy in response to receiving photons (i.e., light). As such, the photovoltaic device  214  may include one or more solar cells. As referenced above, the power conversion devices  210  may include other power conversion devices  216  capable of converting power from one form, such as body heat, movement, or other forms of power to another form (e.g., electricity) for use by the footwear compute device  110 . 
     The illustrative footwear compute device  110  also includes the communication subsystem  218 , which may be embodied as one or more devices and/or circuitry capable of enabling communications with one or more compute devices, such as the step tracker compute device  120 , another footwear compute device  110 , or the server compute device  130 . The communication subsystem  218  may be configured to use any suitable communication protocol to communicate with other devices including, for example, wireless data communication protocols, cellular communication protocols, and/or wired communication protocols. The communication subsystem  218  may include a wireless communication device  220 , a body conductance communication device  222 , and/or other communication devices  224 . The wireless communication device  220  may be any device capable of communicating data (e.g., acceleration data) to another compute device (e.g., the step tracker compute device  120 ) wirelessly. As such, the wireless communication device  220  may transmit data using any wireless data communication protocol, such as Bluetooth, ZigBee, or other wireless communication protocols. The body conductance communication device  222  may be embodied as any device capable of communicating data to another compute device (e.g., the step tracker compute device  120 ) that is in contact with the body of the user, using body conductance (e.g., electrical conductance of the skin of the user). The other communication devices  224  may be embodied as any other types of communication devices capable of communicating data (e.g., acceleration data) to another compute device (e.g., the step tracker compute device  120 ). 
     The footwear compute device  110  may additionally include a data storage device  226 , which may be embodied as any type of device or devices configured for short-term or long-term storage of data such as, for example, memory devices and circuits, memory cards, solid-state drives, hard disk drives, or other data storage devices. The data storage device  226  may store data and software used during operation of the footwear compute device  110  such as acceleration data, operating systems, applications, programs, libraries, and drivers, as described in more detail herein. 
     Referring now to  FIG. 3 , the step tracker compute device  120  may be embodied as any type of compute device capable of performing the functions described herein. For example, the step tracker compute device  120  may be embodied as a computer, wearable compute device, a smartphone, a personal digital assistant, a consumer electronic device, a tablet compute device, a smart appliance, and/or any other compute device capable of analyzing the acceleration data from the footwear compute device(s)  110  to produce step data indicative of steps taken by the user. In the illustrative embodiment, the step tracker compute device  120  includes a processor  302 , a main memory  304 , an input/output subsystem  306 , a communication subsystem  308 , and a data storage  316 . 
     The processor  302  may be embodied as any type of processor capable of performing the functions described herein. For example, the processor may be embodied as a single or multi-core processor(s) having one or more processor cores, a digital signal processor, a microcontroller, or other processor or processing/controlling circuit. Similarly, the main memory  304  may be embodied as any type of volatile or non-volatile memory or data storage capable of performing the functions described herein. In operation, the main memory  304  may store various data and software used during operation of the step tracker compute device  120  such as acceleration data, energy contour data, step data, operating systems, applications, programs, libraries, and drivers. The main memory  304  is communicatively coupled to the processor  302  via the I/O subsystem  306 . 
     The I/O subsystem  306  may be embodied as circuitry and/or components to facilitate input/output operations with the processor  302 , the main memory  304 , and other components of the step tracker compute device  120 . For example, the I/O subsystem  306  may be embodied as, or otherwise include, memory controller hubs, input/output control hubs, firmware devices, communication links (i.e., point-to-point links, bus links, wires, cables, light guides, printed circuit board traces, etc.) and/or other components and subsystems to facilitate the input/output operations. In some embodiments, the I/O subsystem  306  may form a portion of a system-on-a-chip (SoC) and be incorporated, along with the processor  302 , the memory  304 , and other components of the step tracker compute device  120 , on a single integrated circuit chip. 
     The illustrative step tracker compute device  120  also includes the communication subsystem  308 , which may be embodied as one or more devices and/or circuitry capable of enabling communications with one or more compute devices, such as the footwear compute device(s)  110  or the server compute device  130 . The communication subsystem  308  may be configured to use any suitable communication protocol to communicate with other devices including, for example, wireless data communication protocols, cellular communication protocols, and/or wired communication protocols. The communication subsystem  308  may include a wireless communication device  310 , a body conductance communication device  312 , and/or other communication devices  314 . The wireless communication device  310  may be any device capable of communicating data with one or more compute devices such as the footwear compute device(s)  110  and/or the server compute device  130  wirelessly. As such, the wireless communication device  310  may transmit data using any wireless data communication protocol. The body conductance communication device  312  may be embodied as any device capable of communicating data with another compute device (e.g., the footwear compute device(s)  110 ) that are in contact with the body of the user, using body conductance (e.g., electrical conductance of the skin of the user). The other communication devices  314  may be embodied as any other types of communication devices capable of communicating data (e.g., acceleration data or step data) with another compute device (e.g., the footwear compute device(s)  110  and/or the server compute device  130 ). 
     The data storage device  316  may be embodied as any type of device or devices configured for short-term or long-term storage of data such as, for example, memory devices and circuits, memory cards, solid-state drives, hard disk drives, or other data storage devices. The data storage device  316  may store data and software used during operation of the step tracker compute device  120  such as acceleration data, energy contour data, step data, operating systems, applications, programs, libraries, and drivers, as described in more detail herein. 
     The step tracker compute device  120  additionally includes a display  318 . The display may be embodied as, or otherwise use, any suitable display technology including, for example, a liquid crystal display (LCD), a light emitting diode (LED) display, a cathode ray tube (CRT) display, a plasma display, and/or other display usable in a compute device. The display  318  may include a touchscreen sensor that uses any suitable touchscreen input technology to detect the user&#39;s tactile selection of information displayed on the display including, but not limited to, resistive touchscreen sensors, capacitive touchscreen sensors, surface acoustic wave (SAW) touchscreen sensors, infrared touchscreen sensors, optical imaging touchscreen sensors, acoustic touchscreen sensors, and/or other type of touchscreen sensors. The step tracker compute device  120  may additionally include one or more peripheral devices  320 . Such peripheral devices  320  may include any type of peripheral device commonly found in a compute device such as speakers, a mouse, a keyboard, and/or other input/output devices, interface devices, and/or other peripheral devices. 
     Referring back to  FIG. 1 , the server compute device  130  may be embodied as any type of server computer capable of storing and analyzing step data (i.e., determining statistical information, detecting trends, tracking progress towards goals, etc.) from the step tracker compute device  120  and potentially other step tracker compute devices of other users. The server compute device  130  may include components commonly found in a server computer, such as a processor, memory, I/O subsystem, data storage, communication subsystem, etc. Those components may be substantially similar to the corresponding components of the step tracker compute device  120 . As such, further descriptions of the like components are not repeated herein with the understanding that the description of the corresponding components provided above in regard to the step tracker compute device  120  applies equally to the corresponding components of the server compute device  130 . 
     Referring back to  FIG. 1 , the network  140  may be embodied as any number of various wireless or wired networks. For example, the network  140  may be embodied as, or otherwise include, a publicly-accessible, global network such as the Internet, a cellular network, a wireless or wired wide area network (WAN), or a wireless or wired local area network (LAN). As such, the network  140  may include any number of additional devices, such as additional computers, routers, and switches, to facilitate communications among the devices of the system. 
     Referring now to  FIG. 4 , in the illustrative embodiment, the footwear compute device  110  may establish an environment  400  during operation. The illustrative environment  400  includes a data communication module  420 , an acceleration data management module  430 , and a power management module  440 . Each of the modules, logic, and other components of the environment  400  may be embodied as hardware, firmware, software, or a combination thereof. As such, in some embodiments, one or more of the modules of the environment  400  may be embodied as circuitry or collection of electrical devices (e.g., data communication circuitry  420 , acceleration data management circuitry  430 , power management circuitry  440 , etc.). It should be appreciated that, in such embodiments, one or more of the data communication circuitry  420 , the acceleration data management circuitry  430 , and the power management circuitry  440  may form a portion of one or more of the controller  202 , acceleration sensor  208 , power conversion device(s)  210 , communication subsystem  218 , data storage  226 , and/or other components of the footwear compute device  110 . Additionally, in some embodiments, one or more of the illustrative modules may form a portion of another module and/or one or more of the illustrative modules may be independent of one another. Further, in some embodiments, one or more of the modules of the environment  400  may be embodied as virtualized hardware components or emulated architecture, which may be established and maintained by the controller  202  or other components of the footwear compute device  110 . 
     In the illustrative environment  400 , the footwear compute device  110  also includes acceleration data  402  produced using the acceleration sensor  208 . In the illustrative embodiment, the acceleration data  402  indicates acceleration of the footwear compute device  110  in three spatial dimensions over time. The acceleration data  402  may be accessed by the various modules and/or sub-modules of the footwear compute device  110 . It should be appreciated that the footwear compute device  110  may include other components, sub-components, modules, sub-modules, and/or devices commonly found in a compute device, which are not illustrated in  FIG. 4  for clarity of the description. 
     The data communication module  420 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to manage inbound and outbound data communications to and from the footwear compute device  110 , respectively. For example, the data communication module  420  may be configured to transmit the acceleration data  402  to the step tracker compute device  120 . The data communication module  420  may be configured to pair with the step tracker compute device  120  prior to communicating acceleration data to the step tracker compute device  120 . In some embodiments, the data communication module  420  may additionally be configured to pair with another footwear compute device  110 , to receive acceleration data from that footwear compute device  110  and relay the received acceleration data to the step tracker compute device  120 . In the illustrative embodiment, the data communication module  420  is configured to transmit the acceleration data  402  to the step tracker compute device  120  at a predefined interval (e.g., every tenth of a second). Additionally or alternatively, the data communication module  420  may be configured to transmit the acceleration data  402  in response to a query from the step tracker compute device  120 . 
     The acceleration data management module  430 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to interface with the acceleration sensor  208  to receive the acceleration data  402 . In some embodiments, the acceleration data management module  430  may be configured to buffer the received acceleration data  402  until the data communication module  420  transmits the acceleration data  402  to the step tracker compute device  120 . Additionally, the acceleration data management module  430  may be configured to convert data received from the acceleration sensor from one format to another format, such as by converting analog signals (e.g., voltage levels) into digital data, and/or otherwise parse or condition the acceleration data  402  for storage and/or transmission to the step tracker compute device  120 . 
     The power management module  440 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to receive power from the one or more power conversion devices  210  and provide the power to the components of the footwear compute device on an as-needed basis. Further, the power management module  440  may be configured to determine a present level of power provided by the power conversion device(s)  210 , estimate predicted levels of power to be provided by the power conversion device(s)  210 , selectively enable or disable one or more of the power conversion devices  210 , and control power consumption modes (e.g., a high power operational mode, a low power operational mode, a sleep mode, etc.) of various components of the footwear compute device (e.g., the controller  202 , the main memory  204 , etc.). 
     Referring now to  FIG. 5 , in the illustrative embodiment, the step tracker compute device  120  may establish an environment  500  during operation. The illustrative environment  500  includes a data communication module  520 , a step detector module  530 , and a step analysis module  540 . Each of the modules, logic, and other components of the environment  500  may be embodied as hardware, firmware, software, or a combination thereof. As such, in some embodiments, one or more of the modules of the environment  500  may be embodied as circuitry or collection of electrical devices (e.g., data communication circuitry  520 , step detector circuitry  530 , step analysis circuitry  540 , etc.). It should be appreciated that, in such embodiments, one or more of the data communication circuitry  520 , the step detector circuitry  530 , and the step analysis circuitry  540  may form a portion of one or more of the processor  302 , main memory  304 , communication subsystem  308 , data storage  316 , and/or other components of the step tracker compute device  120 . Additionally, in some embodiments, one or more of the illustrative modules may form a portion of another module and/or one or more of the illustrative modules may be independent of one another. Further, in some embodiments, one or more of the modules of the environment  500  may be embodied as virtualized hardware components or emulated architecture, which may be established and maintained by the processor  302  or other components of the step tracker compute device  120 . 
     In the illustrative environment  500 , the step tracker compute device  120  also includes the acceleration data  402  received from the footwear compute device(s)  110 , energy contour data  504 , and step data  506 . As described above, in the illustrative embodiment, the acceleration data  402  indicates acceleration of the footwear compute device  110  in three spatial dimensions over time. The energy contour data  504 , in the illustrative embodiment, is indicative of an amount of energy associated with the acceleration data  402  over time. As described in more detail herein, in the illustrative embodiment, the energy contour data  504  is the result of a conversion performed by the step tracker compute device  120  of the multiple dimensions of the acceleration data  402  over time into a single value (e.g., energy) that varies over time. In the illustrative embodiment, the step data  506  is representative of steps detected by the step tracker compute device  120  based on analyzing the energy contour data  504 , which in turn is produced from the acceleration data  402 , as described in more detail herein. The step data  506  is any data that indicates steps taken by the user in a particular time period (e.g., during a day, over a week, month, year, or episodically, such as during a walk). The step data  506  may also include information indicative of a pace, characteristics of a stride of the user, a determined condition or activity of the user, and/or statistical information pertaining to the detected steps of the user. The acceleration data  402 , energy contour data  504 , and step data  506  may be accessed by the various modules and/or sub-modules of the step tracker compute device  120 . It should be appreciated that the step tracker compute device  120  may include other components, sub-components, modules, sub-modules, and/or devices commonly found in a compute device, which are not illustrated in  FIG. 5  for clarity of the description. 
     The data communication module  520 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to manage inbound and outbound data communications to and from the step tracker compute device  120 , respectively. For example, the data communication module  520  may be configured to receive the acceleration data  402  from each footwear compute device  110  and transmit the step data  506  to the server compute device  130 . The data communication module  520  may be configured to pair with each footwear compute device  110  prior to receiving acceleration data. Additionally, in the illustrative embodiment, the data communication module  520  is configured to communicate the step data  506  to the server compute device  130  for storage and/or analysis (e.g., statistical analysis, goal tracking, etc.). 
     The illustrative step detector module  530 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to analyze the acceleration data  402  received from the footwear compute device(s)  110  and detect the user&#39;s steps from the acceleration data  402 . To do so, in the illustrative embodiment, the step detector module  530  includes an energy contour module  532 , a data refinement module  534 , and a dynamic threshold determination module  536 . The energy contour module  532 , in the illustrative embodiment, is configured to receive the acceleration data  402  as an input and produce the energy contour data  504  as an output. As described above, the acceleration data  402  indicates acceleration in three spatial dimensions over time. The energy contour module  532  may be configured to determine the energy for each instance in time represented in the acceleration data  402  by squaring the acceleration for each spatial dimension and summing the resulting values. As such, the definition of “energy” as used in at least some embodiments described herein may differ from conventional definitions of energy. In the illustrative embodiment, the energy contour module  532  is further configured to compensate for an effect of gravity when calculating the energy contour data  504 , such as by subtracting the acceleration of gravity (i.e.,  9 . 8  meters per second squared) from acceleration data in a dimension that is affected by gravity (i.e., is parallel to gravity, such as the z dimension). 
     In the illustrative embodiment, the data refinement module  534  is configured to remove noise and otherwise prepare the energy contour data  504  for detection of steps. In doing so, the data refinement module  534  is configured to apply a filter, such as a bandpass filter, to remove data associated with frequencies that are not related to a pace at which a human generally walks or runs. In the illustrative embodiment, the data refinement module  534  is configured to apply a bandpass filter that excludes frequencies less than 0.5 Hz and greater than 2 Hz. The data refinement module  534  may also be configured to mask negative values in the filtered energy contour data, such as by setting any negative values to zero. 
     The illustrative dynamic threshold determination module  536  is configured to continually determine a threshold indicative of peaks in the energy contour data  504 . As the user&#39;s pace and gait may change during the course of walking over differing terrain, the peaks in the energy contour data may occur at differing energy values. As described in more detail herein, the dynamic threshold determination module  536  may be configured to perform a sliding window analysis in which the dynamic threshold determination module  536  determines a threshold energy value for any given point in time represented by the energy contour data, based on a set (a “window”) of consecutive energy values preceding and/or succeeding the given point in time. An energy value in the energy contour data  504  that satisfies the dynamic threshold associated with the instant in time associated with that energy value qualifies as a peak. 
     It should be appreciated that each of the energy contour module  532 , the data refinement module  534 , and the dynamic threshold determination module  536  may be separately embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof. For example, the energy contour module  532  may be embodied as a hardware component, while the data refinement module  534  and the dynamic threshold determination module  536  are embodied as virtualized hardware components or as some other combination of hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof. 
     The illustrative step analysis module  540 , which may be embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof as discussed above, is configured to analyze at least the step data  506  to produce one or more determinations regarding the user, such as determining an activity of the user or determining a pace of the user. Further, in the illustrative embodiment, the step analysis module  540  is configured to produce a report of the determination, such as by transmitting the one or more determinations to the server compute device  130  and/or presenting the one or more determinations to the user. To do so, in the illustrative embodiment, the step analysis module  540  includes an activity determination module  542 , a pace determination module  544 , and a data reporter module  546 . In the illustrative embodiment, the activity determination module  542  is configured to determine an activity of the user based on the step data  506 . In the illustrative embodiment, the activity determination module  542  is configured to compare the step data  506  and/or the acceleration data  402  and/or energy contour data  504  to one or more predefined signatures indicative of predefined activities, such as walking, jogging, running, sitting, etc. In some embodiments, the activity determination module  542  may be configured to identify an abrupt change in the orientation of the acceleration represented in the acceleration data as a fall. 
     The pace determination module  544  may be configured to determine an instantaneous pace of the user by counting a number of detected steps over a relatively short period of (e.g., three seconds) and/or determine an average pace of the user over a longer period of time, such as over the course of an exercise session or other time period (e.g., a day, a week, a month, etc.). The data reporter module  546  may be configured to transmit the determination of the activity, the pace, and/or other information associated with the step data  506  to the server compute device  130  and/or present such information to the user, such as in a visual representation through the display  318  or in another format (e.g., an audible report). 
     It should be appreciated that each of the activity determination module  542 , the pace determination module  544 , and the data reporter module  546  may be separately embodied as hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof. For example, the activity determination module  542  may be embodied as a hardware component, while the pace determination module  544  and the data reporter module  546  are embodied as virtualized hardware components or as some other combination of hardware, firmware, software, virtualized hardware, emulated architecture, and/or a combination thereof. 
     Referring now to  FIG. 6 , in use, the footwear compute device  110  may execute a method  600  for monitoring foot movement of the user. The method  600  begins with block  602 , in which the footwear compute device  110  determines whether to monitor foot movement of the user. In the illustrative embodiment, the footwear compute device  110  may determine to monitor foot movement upon performing a self assessment and determining that the footwear compute device  110  has been paired with the step tracker compute device  120  and/or that at least one of the power conversion devices  210  is able to provide sufficient power to the footwear compute device  110  to monitor the foot movement. In other embodiments, the footwear compute device  110  determines whether to monitor foot movement of the user based on other criteria. Regardless, in response to a determination to monitor foot movement of the user, the method  600  advances to block  604 . Otherwise, the method  600  loops back to block  602  to again determine whether to monitor foot movement of the user. In block  604 , the footwear compute device  110  obtains power from one or more of the power conversion devices  210 . In doing so, as indicated in block  606 , footwear compute device  110  may obtain power from the piezoelectric device  212 , such as in response mechanical stress to the piezoelectric device  212  from the user wearing the shoe and impacting the ground. Additionally or alternatively, as indicated in block  608 , the footwear compute device  110  may obtain power from the photovoltaic device  214 , such as in response to the photovoltaic device  214  receiving light from sunlight or another light source. In other embodiments, the footwear compute device  110  may receive power from a different power conversion device  216 . 
     In block  610 , the footwear compute device  110  obtains acceleration data  402  from the acceleration sensor  208 . In doing so, as indicated in block  612 , the footwear compute device  110  may obtain x-axis acceleration data, representing a positive or negative acceleration along an x-axis over time. Additionally, as indicated in block  614 , the footwear compute device  110  may obtain y-axis acceleration data, representing a positive or negative acceleration along a y-axis, which is perpendicular to the x-axis, over time. Further, as indicated in block  616 , the footwear compute device  110  may obtain z-axis acceleration data, representing a positive or negative acceleration along a z-axis, which is perpendicular to both the x-axis and the y-axis, over time. In obtaining the acceleration data  402 , the footwear compute device  110  may convert signals from the acceleration sensor  208  from one format to another format, such as from an analog value (e.g., a voltage level) to a digitally encoded representation of the analog value for each axis. 
     In block  618 , the footwear compute device  110  transmits the obtained acceleration data  402  to the step tracker compute device  120 . In doing so, as indicated in block  620 , the footwear compute device  110  may transmit the obtained acceleration data  402  wirelessly, using the wireless communication device  220 . Alternatively, as indicated in block  622 , the footwear compute device  110  may transmit the obtained acceleration data  402  through the body of the user using body coupled communication (i.e., using the body conductance communication device  222 ). In other embodiments, the footwear compute device  110  may transmit the obtained acceleration data to the step tracker compute device  120  using another type of communication device  224 . After transmitting the acceleration data to the step tracker compute device  120 , the method  600  loops back to block  602  in which the footwear compute device  110  determines whether to continue to monitor foot movement of the user. 
     Referring now to  FIG. 7 , in use, the step tracker compute device  120  may execute a method  700  for tracking steps of the user. In block  702 , the step tracker compute device  120  determines whether to track steps of the user. In doing so, the step tracker compute device  120  may receive a request from the user through a graphical user interface to proceed with tracking steps of the user or may receive the request from another source, such as from the one or more footwear compute devices  110  (e.g., footwear compute devices  112  and  114 ). In other embodiments, the step tracker compute device  120  may determine to track steps of the user based on other criteria. Regardless, if the step tracker compute device  120  determines to track steps of the user, the method advances to block  704 . Otherwise, the method loops back to block  702  to again determine whether to track steps of the user. In block  704 , the step tracker compute device  120  receives the acceleration data  402  from the one or more footwear compute devices  110 . In the illustrative embodiment, as indicated in block  706 , the step tracker compute device  120 , receives the acceleration data  402  in three spatial dimensions (i.e., the x-axis, the y-axis, and the z-axis). As indicated in block  708 , the step tracker compute device  120  may receive the acceleration data  402  wirelessly, such as by using the wireless communication device  310 . Alternatively, as indicated in block  710 , the step tracker compute device  120  may receive the acceleration data  402  through the body of the user, using body coupled communication (i.e., using the body conductance communication device  312 ). 
     In block  712 , the step tracker compute device  120  generates the energy contour data  504  from the acceleration data  402 . In doing so, as indicated in block  714 , the step tracker compute device  120  may determine a combined magnitude of the acceleration in the three spatial dimensions (i.e., x-axis, y-axis, and z-axis) for each instant in time for which the acceleration data includes an acceleration measurement. As indicated in block  716 , the step tracker compute device  120  may compensate for the effect of gravity, such as by subtracting the acceleration of gravity from the acceleration data associated with the pertinent axis (i.e., the z-axis). Accordingly, in the illustrative embodiment, the step tracker compute device  120  may determine each data point in the energy contour data  504  based on Equation 1, shown below:
 
Energy( x   i )= a   x ( x   i ) 2   +a   y ( x   i ) 2 +( a   z ( x   i )− g ) 2   (Equation 1)
 
     In Equation 1, x i  represents the index of the present data point in the data set, a x  represents the acceleration data set for the x-axis, a y  represents the acceleration data set for the y-axis, a z  represents the acceleration data set for the z-axis, and g represents the acceleration of gravity (i.e., 9.8 m/s 2 ). 
     In block  718 , the step tracker compute device  120  refines the energy contour data for further analysis. In doing so, as indicated in block  720 , the step tracker compute device  120  may apply a bandpass filter to the energy contour data  504 . In the illustrative embodiment, the bandpass filter excludes frequencies that fall outside of a predefined range of frequencies that are associated with a human traveling by foot (e.g., 0.5 Hz to 2 Hz). In other embodiments, the step tracker compute device  120  may apply a different type of filter to exclude one or more different frequencies or frequency ranges from the energy contour data  504 . In the illustrative embodiment, as indicated in block  722 , the step tracker compute device  120  masks any negative values present in the energy contour data  504 . To so, the step tracker compute device may identify negative values in the energy contour data  504  and set those values to zero. 
     In block  724 , the step tracker compute device  120  determines dynamic thresholds that are indicative of energy peaks in the energy contour data  504 . In doing so, as indicated in block  726 , the step tracker compute device  120  may determine the dynamic thresholds based on a sliding window analysis. In the illustrative embodiment, the dynamic threshold t is calculated dynamically from a sliding window of size w, from the energy contour data  504 , represented as M(x i ) in the following equations.
 
 t=μ+cσ, X∈R   0   +   (Equation 2)
 
     In Equation 3, shown below, μ represents the mean of M(x i ) across the window length, w. 
     
       
         
           
             
               
                 
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     In Equation 4, provided below, a represents the standard deviation of M(x i ) across the window length, w. 
     
       
         
           
             
               
                 
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     The window length, w, is provided by Equation 5, shown below.
 
 w=α+β+ 1  (Equation 5)
 
     The window range, W, is provided by Equation 6, as follows:
 
 W=[x   i−α   ,x   i+β ]  (Equation 6)
 
     In the above equations, c is a parameter evaluated experimentally and, in the illustrative embodiment, is set to 1.5 so that the threshold level remains just below the energy peak. Parameters α and β represent a lower limit on a distance (e.g., a minimum distance) between consecutive energy peaks. In the illustrative embodiment, both α and β are set to 5, which corresponds to an upper limit (e.g., a maximum) peak repetition every 0.5 seconds for a sampling rate of 10 Hz. 
     After determining the dynamic thresholds, the method advances to block  728 , shown in  FIG. 8 . In block  728 , the step tracker compute device  120  detects steps based on the dynamic energy thresholds and the energy contour data  504  to generate the step data  506 . In the illustrative embodiment, the step tracker compute device  120  is configured to detect a signal instance x j  as a footstep if the presently analyzed data point (e.g., M(x j )) of the energy contour data  504  is the greatest data point in the window, as indicated in block  730 , and if the presently analyzed data point exceeds the threshold t, as indicated in block  732 . This analysis is shown as Equation 7, below. 
     
       
         
           
             
               
                 
                   
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     By determining the dynamic thresholds as described above, the step tracker compute device  120  is able to detect peaks, and thus the user&#39;s steps, in the energy contour data  504  even though the energy associated with one peak at one point in time is different than the energy associated with another peak at a different point in time. In other words, the dynamic threshold calculation enables the step tracker compute device  120  to detect footsteps even as the user&#39;s stride and pace change, and without requiring the user to perform a separate calibration process. 
     In block  734 , the step tracker compute device  120  makes a determination of the subsequent actions to take based on whether it performed the above analysis on acceleration data  402  from multiple footwear compute devices  110  (e.g., footwear compute devices  112 ,  114 ) or just a single footwear compute device  110  (e.g., footwear compute device  112 ). If the step tracker compute device  120  generated step data  506  from acceleration data  402  from multiple footwear compute devices  110 , the method  700  advances to block  736  in which the step tracker compute device  120  compares the step data  506  associated with each footwear compute device  110  to determine whether the number of steps in the step data  506  for one footwear compute device  110  is consistent with the number of steps in the step data  506  for the other footwear compute device  110 . In the illustrative embodiment, the step tracker compute device  120  determines whether the numbers of steps indicated in each set of step data  506  is within a predefined number of steps (e.g., one step) of each other. If the compared step data  506  is not consistent, the step tracker compute device  120  reports an error to the user, such as through the display  318 . Subsequently, the method  700  loops back to block  702  of  FIG. 7  in which the step tracker compute device  120  again determines whether to track steps of the user. 
     Referring back to block  734 , if the step tracker compute device  120  determines that it analyzed acceleration data  402  from only a single footwear compute device  110 , or if the step tracker compute device  120  determines, in block  738 , that the step data  506  is consistent, the method advances to block  742 . In block  742 , the step tracker compute device  120  performs an analysis on the step data  506 . As indicated in block  744 , the step tracker compute device  120  may determine an activity of the user based at least on the step data  506 . In the illustrative embodiment, the step tracker compute device  120  may compare the step data  506  with one or more predefined signatures of step data that are associated with defined activities (e.g., running, jogging, walking, climbing, sitting, etc.) and determine whether the step data  506  matches any of the predefined signatures. If so, the step tracker compute device  120  may determine that the user is performing the activity associated with the matching signature. 
     As indicated in block  746 , the step tracker compute device  120  may determine a pace of movement of the user. In the illustrative embodiment, the step tracker compute device  120  does so by determining the number of steps that have occurred over a predefined time period, as indicated in the step data  506 . As indicated in block  748 , the step tracker compute device  120  may determine whether the user has fallen. In the illustrative embodiment, the step tracker compute device  120  may determine that the user has fallen if the step data  506  indicates an abrupt stop in the pace. The step tracker compute device  120  may additionally analyze the acceleration data  402  to determine whether the acceleration sensor detected a rotation of about 90 degrees, as such an occurrence may be a further indication that the user has fallen. 
     After analyzing the step data  506 , the method  700  advances to block  750  of  FIG. 9 , in which the step tracker compute device  120  reports the step data  506 . In doing so, the step tracker compute device  120  may also transmit the results of the analysis of the step data  506  (e.g., the determined activity, the user&#39;s pace, the determination that the user has fallen, etc.). The step tracker compute device  120  may present the step data  506  to the user. In the illustrative embodiment, as indicated in block  752 , the step tracker compute device  752  presents a visual representation of the step data to the user, such as in a graphical user interface presented on the display  318 . Additionally or alternatively, the step tracker compute device  120  may present the information to the user audibly, or through any other output method. As indicated in block  754 , the step tracker compute device  120  may transmit the step data to the server compute device  130  for analysis (e.g., statistical analysis, goal tracking, etc.) and/or storage. In the event that the step tracker compute device  120  has determined that the user has fallen, the step tracker compute device  120  may transmit this determination to the server compute device  130  which may, in turn, notify emergency personnel to assist the user. 
     Referring now to  FIG. 10 , an article of footwear  1000 , which, in the illustrative embodiment is a shoe, includes the footwear compute device  110 . Components of the footwear compute device  110  may be distributed across various portions of the footwear  1000 . In the illustrative embodiment, the piezoelectric device  212  is located in a heel portion  1010  of the sole of the footwear  1000 . By locating the piezoelectric device  212  in the heel portion  1010 , the piezoelectric device  212  may experience more mechanical stress when the user is walking, jogging, or running, than if the piezoelectric device  212  was located in another portion of the sole. Accordingly, the placement of the piezoelectric device  212  may result in more electrical power generation as compared to other possible locations for the piezoelectric device  212 . Nevertheless, in other embodiments, the piezoelectric device  212  may be located in another portion of the footwear  1000 . In the illustrative embodiment, the acceleration sensor  208  is located in a middle portion  1020  of the sole of the footwear  1000 , as this location provides acceleration data that is more representative of the movement of the footwear  1000  as a whole, as compared to other locations within the footwear  1000 . However, in other embodiments, the acceleration sensor  208  may be located in another portion of the footwear, such as near a toe portion  1030 , as indicated in  FIG. 10 . 
     Referring now to  FIG. 11 , a plot  1100  of the acceleration data  402  over time includes x-axis acceleration data  1110 , y-axis acceleration data  1120 , and z-axis acceleration data  1130 . As described above, in the illustrative embodiment, the footwear compute device  110  is configured to transmit the acceleration data  402  to the step tracker compute device  120  for use in detecting the user&#39;s steps. Referring now to  FIG. 12 , a plot  1200  of the energy contour data  504 , which may be produced and analyzed by the step tracker compute device  120 , combines the acceleration data for the multiple spatial dimensions (e.g., x-axis, y-axis, and z-axis) into a set of one dimensional energy values  1210  that vary over time. Referring now to  FIG. 13 , a plot  1300  includes the energy contour data  1310  over time after the step tracker compute device  120  has applied a bandpass filter that excludes frequencies below 0.5 Hz and above 2.0 Hz. Once the bandpass filter has been applied, the energy contour data may contain negative values. Referring now to  FIG. 14 , a plot  1400  includes the energy contour data  1410  over time after the step tracker compute device  120  has masked the negative values present in the energy contour data  1310  of  FIG. 13 . In the illustrative embodiment, the step tracker compute device  120  is configured to mask the negative values by setting them to zero, as described above. Referring now to  FIG. 15 , a plot  1500  includes the energy contour data  1410  after the bandpass filter and negative masking have been applied. The plot  1500  additionally includes the dynamic thresholds  1510  as well as steps  1520  detected by the step tracker compute device  120  at points where the energy contour data exceeds the dynamic thresholds  1510 . As shown, the dynamic thresholds  1510  change over time, selectively increasing or decreasing, in response to changes in the user&#39;s stride. As described above, by producing the dynamic thresholds, the step tracker compute device  120  is able to detect steps of the user as the user changes his or her stride, without requiring the user to perform a separate calibration or recalibration process with the step tracker compute device  120 . 
     EXAMPLES 
     Illustrative examples of the technologies disclosed herein are provided below. An embodiment of the technologies may include any one or more, and any combination of, the examples described below. 
     Example 1 includes a step tracker compute device for tracking steps of a user, comprising a data communication module to receive acceleration data indicative of movement of a foot of the user; and a step detector module to (i) generate, based on the received acceleration data, energy contour data indicative of energy levels over time, (ii) determine dynamic energy thresholds indicative of peaks in the energy contour data, and (iii) detect steps of the user based on the dynamic energy thresholds and the energy contour data to generate step data. 
     Example 2 includes the subject matter of Example 1, and wherein the step detector module is further to apply a bandpass filter to the energy contour data before the determination of the dynamic energy threshold. 
     Example 3 includes the subject matter of any of Examples 1 and 2, and wherein to apply a bandpass filter comprises to apply a bandpass filter that excludes frequencies less than 0.5 Hz and frequencies greater than 2 Hz. 
     Example 4 includes the subject matter of any of Examples 1-3, and wherein the step detector module is further to mask negative values in the filtered energy contour data. 
     Example 5 includes the subject matter of any of Examples 1-4, and wherein to determine a dynamic energy threshold comprises to determine a first energy threshold value associated with a first window of energy contour data associated with a first time period; and determine a second energy threshold value associated with a second window of energy contour data associated with a second time period. 
     Example 6 includes the subject matter of any of Examples 1-5, and wherein to generate the energy contour data comprises to determine a combined magnitude of acceleration in three spatial dimensions. 
     Example 7 includes the subject matter of any of Examples 1-6, and wherein the step detector module is further to compensate for an effect of gravity in the acceleration data. 
     Example 8 includes the subject matter of any of Examples 1-7, and wherein to receive the acceleration data comprises to receive the acceleration data transmitted from a footwear compute device through a body of the user. 
     Example 9 includes the subject matter of any of Examples 1-8, and wherein to receive the acceleration data comprises to receive the acceleration data transmitted wirelessly from a footwear compute device located in footwear worn by the user. 
     Example 10 includes the subject matter of any of Examples 1-9, and further including a step analysis module to analyze the step data to determine an activity of the user. 
     Example 11 includes the subject matter of any of Examples 1-10, and further including a step analysis module to analyze the step data to determine a pace of movement of the user. 
     Example 12 includes the subject matter of any of Examples 1-11, and further including a step analysis module to present a visual representation of the step data to the user. 
     Example 13 includes the subject matter of any of Examples 1-12, and wherein the data communication module is further to transmit the step data to a server compute device for analysis. 
     Example 14 includes the subject matter of any of Examples 1-13, and wherein the acceleration data is a first set of acceleration data associated with movement of one foot of the user over a time period, the data communication module is further to receive a second set of acceleration data associated with movement of the other foot of the user over the time period, and the step detector module is further to generate the step data based on the first set of acceleration data and the second set of acceleration data. 
     Example 15 includes the subject matter of any of Examples 1-14, and wherein the step analysis module is further to determine, based on the acceleration data, whether the user has fallen. 
     Example 16 includes a method for tracking steps of a user, comprising receiving, by a step tracker compute device, acceleration data indicative of movement of a foot of the user; generating, by the step tracker compute device and based on the received acceleration data, energy contour data indicative of energy levels over time; determining, by the step tracker compute device, dynamic energy thresholds indicative of peaks in the energy contour data; and detecting, by the step tracker compute device, steps of the user based on the dynamic energy thresholds and the energy contour data to generate step data. 
     Example 17 includes the subject matter of Example 16, and further including applying, by the step tracker compute device, a bandpass filter to the energy contour data before the determination of the dynamic energy threshold. 
     Example 18 includes the subject matter of any of Examples 16 and 17, and wherein applying a bandpass filter comprises applying a bandpass filter that excludes frequencies less than 0.5 Hz and frequencies greater than 2 Hz. 
     Example 19 includes the subject matter of any of Examples 16-18, and further including masking, by the step tracker compute device, negative values in the filtered energy contour data. 
     Example 20 includes the subject matter of any of Examples 16-19, and wherein determining a dynamic energy threshold comprises determining a first energy threshold value associated with a first window of energy contour data associated with a first time period; and determining a second energy threshold value associated with a second window of energy contour data associated with a second time period. 
     Example 21 includes the subject matter of any of Examples 16-20, and wherein generating the energy contour data comprises determining a combined magnitude of acceleration in three spatial dimensions. 
     Example 22 includes the subject matter of any of Examples 16-21, and further including compensating for an effect of gravity in the acceleration data. 
     Example 23 includes the subject matter of any of Examples 16-22, and wherein receiving the acceleration data comprises receiving the acceleration data transmitted from a footwear compute device through a body of the user. 
     Example 24 includes the subject matter of any of Examples 16-23, and wherein receiving the acceleration data comprises receiving the acceleration data transmitted wirelessly from a footwear compute device located in footwear worn by the user. 
     Example 25 includes the subject matter of any of Examples 16-24, and further including analyzing, by the step tracker compute device, the step data to determine an activity of the user. 
     Example 26 includes the subject matter of any of Examples 16-25, and further including analyzing, by the step tracker compute device, the step data to determine a pace of movement of the user. 
     Example 27 includes the subject matter of any of Examples 16-26, and further including presenting, by the step tracker compute device, a visual representation of the step data to the user. 
     Example 28 includes the subject matter of any of Examples 16-27, and further including transmitting, by the step tracker compute device, the step data to a server compute device for analysis. 
     Example 29 includes the subject matter of any of Examples 16-28, and wherein the acceleration data is a first set of acceleration data associated with movement of one foot of the user over a time period, the method further comprising receiving, by the step tracker compute device, a second set of acceleration data associated with movement of the other foot of the user over the time period; and generating, by the step tracker compute device, the step data based on the first set of acceleration data and the second set of acceleration data. 
     Example 30 includes the subject matter of any of Examples 16-29, and further including determining, by the step tracker compute device and based on the acceleration data, whether the user has fallen. 
     Example 31 includes one or more computer-readable storage media comprising a plurality of instructions that, when executed, cause a compute device to perform the method of any of Examples 16-30. 
     Example 32 includes a step tracker compute device comprising means for receiving acceleration data indicative of movement of a foot of the user; means for generating, based on the received acceleration data, energy contour data indicative of energy levels over time; means for determining dynamic energy thresholds indicative of peaks in the energy contour data; and means for detecting steps of the user based on the dynamic energy thresholds and the energy contour data to generate step data. 
     Example 33 includes the subject matter of Example 32, and further including means for applying a bandpass filter to the energy contour data before the determination of the dynamic energy threshold. 
     Example 34 includes the subject matter of any of Examples 32 and 33, and wherein the means for applying a bandpass filter comprises means for applying a bandpass filter that excludes frequencies less than 0.5 Hz and frequencies greater than 2 Hz. 
     Example 35 includes the subject matter of any of Examples 32-34, and further including means for masking negative values in the filtered energy contour data. 
     Example 36 includes the subject matter of any of Examples 32-35, and wherein the means for determining a dynamic energy threshold comprises means for determining a first energy threshold value associated with a first window of energy contour data associated with a first time period; and means for determining a second energy threshold value associated with a second window of energy contour data associated with a second time period. 
     Example 37 includes the subject matter of any of Examples 32-36, and wherein the means for generating the energy contour data comprises means for determining a combined magnitude of acceleration in three spatial dimensions. 
     Example 38 includes the subject matter of any of Examples 32-37, and further including means for compensating for an effect of gravity in the acceleration data. 
     Example 39 includes the subject matter of any of Examples 32-38, and wherein the means for receiving the acceleration data comprises means for receiving the acceleration data transmitted from a footwear compute device through a body of the user. 
     Example 40 includes the subject matter of any of Examples 32-39, and wherein the means for receiving the acceleration data comprises means for receiving the acceleration data transmitted wirelessly from a footwear compute device located in footwear worn by the user. 
     Example 41 includes the subject matter of any of Examples 32-40, and further including means for analyzing the step data to determine an activity of the user. 
     Example 42 includes the subject matter of any of Examples 32-41, and further including means for analyzing the step data to determine a pace of movement of the user. 
     Example 43 includes the subject matter of any of Examples 32-42, and further including means for presenting a visual representation of the step data to the user. 
     Example 44 includes the subject matter of any of Examples 32-43, and further including means for transmitting the step data to a server compute device for analysis. 
     Example 45 includes the subject matter of any of Examples 32-44, and wherein the acceleration data is a first set of acceleration data associated with movement of one foot of the user over a time period, the step tracker compute device further comprising means for receiving a second set of acceleration data associated with movement of the other foot of the user over the time period; and means for generating the step data based on the first set of acceleration data and the second set of acceleration data. 
     Example 46 includes the subject matter of any of Examples 32-45, and further including means for determining, based on the acceleration data, whether the user has fallen. 
     Example 47 includes a footwear compute device for generating foot movement data of a user, comprising a three dimensional acceleration sensor to generate acceleration data in three dimensions; a power conversion device to receive power in a first form and convert the power to a second form to provide power to the footwear compute device; and a data communication circuit to transmit the acceleration data to a step tracker compute device. 
     Example 48 includes the subject matter of Example 47, and wherein at least a portion of the footwear compute device is incorporated into a shoe. 
     Example 49 includes the subject matter of any of Examples 47 and 48, and wherein the acceleration sensor is incorporated into a middle portion of the shoe. 
     Example 50 includes the subject matter of any of Examples 47-49, and wherein the power conversion device is incorporated into a heel portion of the shoe. 
     Example 51 includes the subject matter of any of Examples 47-50, and wherein the data communication circuit is to transmit the acceleration data through the body of the user to the step tracker compute device. 
     Example 52 includes the subject matter of any of Examples 47-51, and wherein to transmit the acceleration data through the body of the user comprises to transmit the acceleration data using body coupled communication. 
     Example 53 includes the subject matter of any of Examples 47-52, and wherein the data communication circuit is to transmit the acceleration data to the step tracker compute device wirelessly. 
     Example 54 includes the subject matter of any of Examples 47-53, and wherein the power conversion device is a piezoelectric transducer. 
     Example 55 includes the subject matter of any of Examples 47-54, and wherein the power conversion device is a photovoltaic device. 
     Example 56 includes the subject matter of any of Examples 47-55, and further including an acceleration data management module to receive the acceleration data from the three dimensional sensor. 
     Example 57 includes the subject matter of any of Examples 47-56, and further including a power management module to receive power from the power conversion device in the second form and provide the power to the footwear compute device. 
     Example 58 includes a method for generating foot movement data of a user, comprising generating, by a three dimensional acceleration sensor of a footwear compute device, acceleration data in three dimensions; receiving, by a power conversion device of the footwear compute device, power in a first form and converting the power to a second form to provide power to the footwear compute device; and transmitting, by a data communication circuit of the footwear compute device, the acceleration data to a step tracker compute device. 
     Example 59 includes the subject matter of Example 58, and wherein transmitting the acceleration data comprises transmitting the acceleration data through the body of the user to the step tracker compute device. 
     Example 60 includes the subject matter of any of Examples 58 and 59, and wherein transmitting the acceleration data through the body of the user comprises transmitting the acceleration data using body coupled communication. 
     Example 61 includes the subject matter of any of Examples 58-60, and wherein transmitting the acceleration data comprises transmitting the acceleration data to the step tracker compute device wirelessly. 
     Example 62 includes one or more computer-readable storage media comprising a plurality of instructions that, when executed, cause a compute device to perform the method of any of Examples 58-61. 
     Example 63 includes a footwear compute device comprising means for generating acceleration data in three dimensions; means for receiving power in a first form and converting the power to a second form to provide power to the footwear compute device; and means for transmitting the acceleration data to a step tracker compute device. 
     Example 64 includes the subject matter of Example 63, and wherein the means for transmitting the acceleration data comprises means for transmitting the acceleration data through the body of the user to the step tracker compute device. 
     Example 65 includes the subject matter of any of Examples 63 and 64, and wherein the means for transmitting the acceleration data through the body of the user comprises means for transmitting the acceleration data using body coupled communication. 
     Example 66 includes the subject matter of any of Examples 63-65, and wherein the means for transmitting the acceleration data comprises means for transmitting the acceleration data to the step tracker compute device wirelessly.