It may depend on which state, and sometimes it's a grey area if the car is jointly owned (since you could argue the "owner is consenting" to the tracking). htt

It may depend on which state, and sometimes it's a grey area if the car is jointly owned (since you could argue the "owner is consenting" to the tracking). http://www.slate.com/articles/technology/technology/2012/11/gps_trackers_to_monitor_cheating_spouses_a_legal_gray_area_for_private_investigators.html http://www.slate.com/articles/technology/technology/2012/11/...