1. A method comprising: by one or more processors: collect motion and physiological sensor data of a user from one or more sensors worn by the user, the sensor data comprising one or more sensor data vectors; generate an activity signature based on the sensor data; determine whether a signature match exists between the activity signature and a known activity signature associated with an activity type from a set of known activity signatures: if the signature match exists, recognize a known activity type; if the signature match does not exist, generate an unknown activity type based on the one or more sensor data vectors.