Craig...Love the humour!
Someone suggested fit a secret switch. Not with any reference to that but simply by way of interest I worked for a South African company that designed and built all manor of car security systems. Not my division but i saw all the developments. We were commissioned by Mercedes in SA to build a thief proof system including secret switches, fuel and power cut devices, you name it, the works. Remember now, South Africa is one of the top 3 car theft countries in the world. Anyway after preparing a vehicle it was put to the test by a ex professional thief. He drove away in about 90 seconds.
As a result we focused on remote control alarm systems typical of many around today, which was fine for a few months till thieves figured if they stood within range with a monitor they could catch the code then use it at their leisure to steal the car.
We responded by coming up with what was a novel system back then, code hopping. The system transmitted a code then an algorithm changed it so that next time it was different. They soon enough sorted that.
Today as some my know, thieves don't bother to steal a car, all they do is hijack them with guns etc in the street, sometimes with loss of life. There used to be a YouTube video of that test case I spoke of but it seems to have gone however I found a novel solution some bloke has developed to counter hijackings.
https://www.youtube.com/watch?v=aLhWzMOccTg
Let's just hope that things never get that bad here!