Hi Paul,
I'm sure you'll get lots of feedback and ideas on this. An alternative solution would be to install a battery cut-off switch. I just ordered a keyed switch and plan to install it behind the passenger seat (I have a trunk mounted battery). I like the idea of being able to reach over and remove the key as an additional theft deterent. Of course, this would not be automatic, you'd have to reach over and turn the key to cut the power. Here is what I bought...
The Little Switch - With Mounting Bracket - FR1002 - 584 - 5470
Regards,
Kevin