A mobile device includes a motion detector, a processing unit, and a wireless positioning module. The motion detector is configured to detect a motion of the mobile device to obtain a motion signal. The processing unit is configured to do the followings: process the motion signal to obtain a vibration frequency and a vibration regularity of the mobile device; determine a device activity status of the mobile device according to the vibration frequency and the vibration regularity; and generate a control signal when finding that the device activity status switches from a first activity status to a second activity status. The wireless positioning module is configured to identify a first location of the mobile device in response to the control signal.