We're considering the "LoJack" system, it's considered the best!
It will tell you if someone is moving your AS and if they do, the police will be able to tract their every move thanks to the satellite locator. Which by the way it's installed every time in a new position. You may even chose where and together with the installer will be the only person to know.
See if it works for you:
http://www.lojack.com/foryou/products.htm
As they say: "better safe than sorry"
Cheers
Kimili