A navigation system includes a communication port in a vehicle, a hand held portable unit, and a wireless communication between the portable unit and the communication port when the portable unit is in the vehicle. A restraint bar 16 is detachably connected to the body support and in turn adjustably carries a tray 18 enabling the tray to be moved toward and away form the back and to be mounted at different angles with respect to the body support 14. Electrodes are placed in the openings at either end of the channel and an electrical power supply is connected to the electrodes.