Looks like it would need to plug into and OBD2 port, so that wouldn't work on old cars. How about an Apple air Tag with a charger hooked to it and hidden up under the dash?
Ultimately i believe that is what ill end up with. Oddly, i don't have an iphone, but everyone i know does....or.......i get one. The ol galaxy note5 has done well..... and doesn't listen to me.
