[Polynikes]

That won't help. The type of people who resort to this type of things would have no problems gaining access to a garage. A better counter measure probably would be to drive a variety of cars or be driven and preferably a car that has little to no computer controlled systems such as early 70’s models

[JoeFromSidney]

a car that has little to no computer controlled systems such as early 70’s models

The problem is not so much computers as radio access to the car, through something like OnStar. Without that radio access, direct access would be necessary. Radio access makes takeover possible without direct access.