I agree, there is a company in my city that will hook a device up to the car battery and place it in a discrete location. They mostly deal with fleet management but some of their business is from spouses tracking each other. There a "funny" story about a wife bringing in a vehicle that her husband had brought in earlier.

A family member works for a large chain of car dealerships. They regularly buy vehicles at auction. It's not uncommon that they find trackers on the vehicles. Here's a picture of one he sent me to play with a couple years ago.

The battery pack on the left, and the tracker on the right were in a magnetic Pelican case attached to the underside of a black Escalade. The sim in the tracker was from some US MVNO that I didn't recognize.

https://i.imgur.com/VLzTPt4.jpg

Hilarious. No problem for the company, but I wonder if they installed two or just sent the data to both of them...

I have a car I don't use very often and often forget where I park it. DX and BangGood have GPS trackers you can buy for $20-40 that you can install a prepaid SIM card in, text message and receive coordinates. Not a bad roll-your-own-LoJack.

That can't possibly be legal.

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/...

Not everybody lives in the USA.

Most people lives in China

Technically he didn't say anything about the United States.

Your friend overpaid for that service. You can purchase an OBD-II dongle that records this information for $80 and $20/mo. So, $100 for 1 month.