## 2 Related Work  
### E-Health Applications  
E-Health applications are gaining popularity and greater acceptance because of their versatility and reduction of care-taking costs. Nowadays diverse systems and health-centered applications are being developed, which according to their application can be categorized in: daily living activities, fall and movement detection, location tracking, medication intake and medical status monitoring [6]. Applications for daily living activities focus on monitoring the activities of individuals within a predetermined space. One important example of this type of project is _AICO_, which utilizes a sophisticated combined Bayesian network that includes the input from a series of environmental parameters that can create an approximation of the activities being carried out by an individual [7]. Another application of this kind is _Caregiver's Assistant_, which employs RFID cards and a database that includes 38,000 human activities and a fast inference mechanism that allows persons to identify the actions of others remotely within a given space [8]. Applications that focus on fall and movement detection focus on following user movements and detecting falls. One example of this kind of service is _Smart HCN_, which consists of a WSN that monitors the posture of the subject and images taken by cameras to alert a specialist if the subject has suffered an accident [9]. Another example of an application that focuses on fall and movement detection is presented in work done by [10], which uses an accelerometer located at head-height to transmit data that can detect a fall and send a notification to a mobile personal digital assistant. Location tracking applications are based mainly on the principle of identifying the location of users and analyzing their behavior. One example of this kind of application is presented in work done by [11]. This system employs a WSN to obtain RSSI values, which, through an algorithm, can locate the location of users within their homes. _ZUPS_ is also an application that centers on location tracking for aged and/or disabled people. This project uses a ZigBee network and ultrasound-positioning systems, which allows caregivers to not only locate individuals within a specified space, but to also provide assistance for persons moving from one place to another beyond the confines of their home [12]. Medication intake applications consist mainly in monitoring the intake of the patient's drugs. _iCabiNET_ provides a solution that employs a smart medicine manager that can notify patients via SMS or audio alarms at home to remind patients about their medications, as well as dosages and times [13]. Another medication intake application by the name of _iPackage_ consists of medication wrappers with RFID tags which can be detected by an RFID sensor at the moment of ingestion, allowing caregivers to remotely monitor whether or not a patient is adhering to instructions [14]. Finally, medical status monitoring collects clinical variables (_i.e._, heart rate, glucose monitoring, pulse, _etc._), elaborates a current-state diagnosis of the patient and provides the information to caretakers. If any abnormality is detected, it can be immediately communicated to either family members or caretakers. _AlarmNet_ is an application that monitors a series of physiological variables, storing the data and processing the information to detect any abnormalities. If an abnormality is found, it notifies a mobile assistant [15]. _Baby Glove_ is an application that monitors vital signs of newborn babies, such as their body temperature. The data is gathered through the baby's romper and then transmitted to a WSN, which constantly supervises important physiological variables and notifies caregivers if there is reading beyond the programmed limits in real time [16].