You know, there used to be things that you can buy to stop burglars:

Little spikes that you put under your seat... well I say "little" - they're a few feet long. As soon as someone sits on the seat activating the pressure pad on it, the spike punches up through the seat and, well, you get the picture. But, of course, there's a little code box thing that you enter a code into to turn the spike off. Therefor, a car theif who doesn't know the code, or that the spike is there will sit on the seat and BAM! Instant Kebab.