You could rig it so your fuel pump will only turn on if your rear winshield wiper is on, that's not real hard, this way it would be much harder to steal.

Easiest way I'd say to do that would be to use a relay at the fuel pump, and have the switched power tapped into the wire running to the rear winshield wiper motor. I'd say no more then like 10 bucks in parts and maybe at most 40 mins to do it.

If you need some more help, let me know, I'd be happy to any way I can.

Later,
Aj