The present invention provides a tracker and the operation process thereof. In one aspect, the tracker, designed for positioning on a part below a users knee, provided in the present invention is able to switch between modes such as walking mode, cycling mode, swimming mode, sleeping mode, and other modes by detecting the motions of a user. By the sensing unit included in the tracker, the tracker can further detect signatures, such as steps taken, distance traveled, stairs climbed, calories burned, cycling speed, swimming type, or heart rate, of a user. Furthermore, the tracker in the present invention is able to synchronize or stream information with other devices. In another aspect, the tracker in the present invention is able to control avatars of a game on other devices as a sensory tool.
