Originally Posted by L-Pink

OnStar can remotely unlock your car, tell police where it is and how fast it's going and even remotely slow down and stop the vehicle for the police, automatically notifies police if you have an accident and the severity of the accident based on speed, airbag deployment and other sensors, it can also run remote system diagnosis on engine/drivetrain, etc.

I'm sure they can tell if work is preformed without being plugged into a dealership computer. And that's just for GM products.