My buddy has a really sweet kill-switch on his 95 camaro... The turn signal control arm on chevy's also houses the cruise control... um, controls. On the very end of the arm is a button that activates the "coast" option, but he's also wired it in to his ignition. When you're driving it works normally, but the car won't start unless it's depressed. The sweet thing is that because of it's location, it's really convenient to press, and it's very easily missed by the casual observer.
I've been trying to figure out a good place like this put put the switch on mine. So far I have a few ideas, but nothing really like yet.