a "friend" of my buddy didnt trust his wife much. he hot wires a cell phone into the engine bay and attached it to a pre-paid cell phone with gps and hid it in a funnel with a rap over it so she wouldnt she it. he was able to trace the phone and caught her partying with a couple other guys....... not sure which one would be cheaper but the prices of prepaid phones nowadays it might be the better option and youll always have a cellphone on hand if yours ever dies or gets lost