A device for recognizing activity of an object. The device comprises a housing configured to be attached to the object and a processing unit disposed in the housing comprising a processor and a movement sensor. The movement sensor measures a signal related to movement of the object during a time window. The processor assigns at least one preliminary activity label to the time window based on at least one numerical descriptor computed from the signal. The processor then determines whether to perform additional analysis dependent upon at least the preliminary activity label. The processor then assigns a final activity label to the time window.