The best hidden switch that I've seen was sitting in the driver's seat the whole time. Working a Jiffy Lube years ago, I couldn't start a customer's truck. He came out to his truck, and told me to touch a specific screw on the dash while turning the ignition. It started. I was the switch! The screw was insulated from ground. By touching it with one hand and any metal with the other, I provided ground for a lower current circuit which tripped a relay in his ignition system. You could get the parts at radio shack.
David
