Cars nowadays send lots of data to the manufacturer through a cellular data connection. A proposal in Massachusetts would require manufacturers to give users access to that data — through a nonfree app.

Yuck! This is oppressive practice of the Internet of Stings: making you communicate with the products you own via the manufacturer's server.

The cellular data connection enables the phone network to track the car's movements, but it wouldn't surprise me if the data includes GPS location. (Does anyone know for a fact?)

The right thing to require is that the car offer a data-only interface, such as a slot to put a memory chip into and the car will write the data on it. This way you could show that data to an independent repair shop when you want to, even though you disconnected the cellular data antenna and the GPS antenna just after you bought the car.