A system provides on-demand operation of a mobile electronic device mounted on a vehicle such as a shopping cart. The system includes a detector for sensing movement of the vehicle and device. Further, the system includes a controller electronically connected to the detector and to the device. With this interconnection, the controller may switch the device between an operating state and a resting state. Specifically, the controller establishes the operating state upon initiation of movement of the device. Also, the system is provided with a timer that is connected to the controller for switching the device to the resting state after expiration of an uninterrupted pre-determined time interval.