It sounds like lots of the ideas rely on a hidden toggle switch. Great, but what if a person gets lazy the one time someone decides to steal your pride, you didn't hit the switch?
My comment earlier was in respect to a fob that did that for you. It could be hidden in the dash out of reach and you could install an override toggle in the engine bay to bypass it if it ever fails. The fob is on your key ring.
As mentioned, it could be set up to interrupt ignition, fuel pump (if electric) or even crank with a relay if you wanted.
Here's an example. Wouldn't mind spending more if a higher quality was available.