There is an auto alarm company that has a wireless proximity sensor
you hide under the dash or plastic of the steering column cover.   (I
have misplaced their web link but I'll post it when I dig it up).

With their system, the vehicle will only start if you have a chip on
your keychain that communicates to the sensor.  If you have the key
without the chip, your van won't start.  I like this idea since you
don't have to remember to flip a hidden switch etc and everything is
hidden.

I want to modify their system and hook it into the fuel pump instead
of the starter, but with a 2 minute or so timer.

i.e. Mr. Thief starts the van with a key or screwdriver, starts
driving then 2 minutes later the van just dies due to fuel starvation
(Won't happen to you with the chip on your keychain).

This way the thief doesn't suspect anything and they think they are
getting away, but they end up having to leave the van in the middle
of the road when it dies of fuel starvation...easy to find within a 2
minute radius of where you parked it...and the thief will probably
think "frigging VW P.O.S, I'll go steal a Ford instead"

-Paul