Mobile wireless device(s) roam within and between premises and a vehicle or other mobile platform and interface to wireless local area networks within the premises or vehicle. When using the intra-vehicular network, a communication relay within the vehicle routes communications from the wireless device to a wide area wireless network such as cellular network or satellite network. This allows the power consumption of the mobile wireless device to be greatly reduced as the mobile device need only communicate with the local intra-vehicular WLAN. The vehicle acts as the power supply for the relay. When the coverage area of the intra-vehicular WLAN overlaps that of another WLAN, seamless handoff allows continuous data or voice connectivity between the overlapping wireless networks.