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. The portable unit has a position locator and is capable of establishing a geographical position of the portable unit. The portable unit is removable from the vehicle by an occupant of the vehicle. An information display may be disposed on, at or within an interior rearview mirror assembly of the vehicle, and may display navigational information for viewing by a driver of the vehicle. The navigational information may be derived from the wireless communication between the portable unit and the communication port.