I use a Ravelco device in my work vans since I'm on the road quite a bit. It's hard to explain, but it's essentially a second key that controls 2 devices such as the ingition box, fuel pump, or starter. There are no two alike so there are no master pinouts for a thief to get hold of either. If you want to read up on it here is a link to their site.
http://www.ravelco.com/index.html
