[benmunger]

Simple barbaric and direct solution...

You could just put a relay in the headlight wiring in the engine bay. Have the relay close when the ignition is on. But of course you would NEVER beable to turn your lights on when the car is off. (getting more complicated, you could put a bypass swith in to bypass the relay)

EDIT: Dont do this. Im a space bum. Forgot that there are other lights on the car. :)