A unitary apparatus configured to be worn on a user, comprising: a processor; a sensor configured to capture motion data of the user; a non-transitory computer-readable medium comprising computer-executable instructions that when executed by the processor perform at least: capturing, from the sensor while being worn by the user, a data stream comprising one or more data points generated as a result of a motion of the user; transforming the one or more data points into a dataset representing a motion of the user; without classifying the one or more data points into an activity type, calculating one or more motion attributes from the dataset: comparing the calculated one or more motion attributes to motion attributes of a plurality of models comprising motion data from a plurality of individuals; selecting, based on a result of the comparing the calculated one or more motion attributes to the motion attributes of the plurality of models, a model, from the plurality of models, as a best-match to the calculated one or more motion attributes; and calculating, using the selected model, an energy expenditure characteristic associated with the motion of the user; determining, using the calculated one or more motion attributes, whether the user is walking or running, wherein: responsive to determining that the user is running, sending the calculated one or more motion attributes to a running model; and responsive to determining that the user is walking, sending the calculated one or more motion attributes to a walking model; and receiving, from the running model or the walking activity model, a speed of the user. a processor; a sensor configured to capture motion data of the user; a non-transitory computer-readable medium comprising computer-executable instructions that when executed by the processor perform at least: capturing, from the sensor while being worn by the user, a data stream comprising one or more data points generated as a result of a motion of the user; transforming the one or more data points into a dataset representing a motion of the user; without classifying the one or more data points into an activity type, calculating one or more motion attributes from the dataset: comparing the calculated one or more motion attributes to motion attributes of a plurality of models comprising motion data from a plurality of individuals; selecting, based on a result of the comparing the calculated one or more motion attributes to the motion attributes of the plurality of models, a model, from the plurality of models, as a best-match to the calculated one or more motion attributes; and calculating, using the selected model, an energy expenditure characteristic associated with the motion of the user; determining, using the calculated one or more motion attributes, whether the user is walking or running, wherein: responsive to determining that the user is running, sending the calculated one or more motion attributes to a running model; and responsive to determining that the user is walking, sending the calculated one or more motion attributes to a walking model; and receiving, from the running model or the walking activity model, a speed of the user. capturing, from the sensor while being worn by the user, a data stream comprising one or more data points generated as a result of a motion of the user; transforming the one or more data points into a dataset representing a motion of the user; without classifying the one or more data points into an activity type, calculating one or more motion attributes from the dataset: comparing the calculated one or more motion attributes to motion attributes of a plurality of models comprising motion data from a plurality of individuals; selecting, based on a result of the comparing the calculated one or more motion attributes to the motion attributes of the plurality of models, a model, from the plurality of models, as a best-match to the calculated one or more motion attributes; and calculating, using the selected model, an energy expenditure characteristic associated with the motion of the user; determining, using the calculated one or more motion attributes, whether the user is walking or running, wherein: responsive to determining that the user is running, sending the calculated one or more motion attributes to a running model; and responsive to determining that the user is walking, sending the calculated one or more motion attributes to a walking model; and responsive to determining that the user is running, sending the calculated one or more motion attributes to a running model; and responsive to determining that the user is walking, sending the calculated one or more motion attributes to a walking model; and receiving, from the running model or the walking activity model, a speed of the user.