My kill switch is hidden. No idea if it has stopped anyone but I still have the car. Sometimes hiding it in plain sight is the best way.
It can be as complex as andy suggests or it can simply kill the circut between the key and the MSD or the key and the coil.
The placement of this thread is probably limiting interest, aside from guys with 400-500 hp not needing nitros these are really cool. With other sticker options they should be a hit. Do you sell the switches without the plate DC12VoltGuy?
Most people here have a sheetmetal dash with terribly expensive corinthian
leather covering it and they may be less inclined to want the plate. Where in N. Cal are you?