Embodiments of the present invention provide a wireless appliance for monitoring a vehicle. The wireless appliance includes a microprocessor configured to select a vehicle-communication protocol of a host vehicle, and then communicate with the host vehicle through the vehicle-communication protocol. The appliance also includes a vehicle-communication circuit, in electrical communication with the microprocessor, which collects diagnostic data from the host vehicle using the vehicle-communication protocol. A GPS module, also in electrical communication with the microprocessor, generates location-based data. For transmitting these data, the appliance includes a first wireless transmitter operating on a terrestrial network and a second wireless transmitter operating on a satellite network. The microprocessor selects the first or second wireless transmitter for transmitting the diagnostic and location-based data.