An apparatus, article, and system, the apparatus including a housing, a 3-axis accelerometer contained in the housing, a medium storing program instructions, and a processor to execute the program instructions stored in the memory to receive a signal from the 3-axis accelerometer indicative of a user's activities, extract features from the received signals, classify the extracted features into a plurality of activity types, determine a total energy expenditure based on the classification of the extracted features； and provide a report of the total energy expenditure.
