I put mine on my 3 door so that if I moved the seat it would trip and I had to reset it each time I got into the car.

Literally the same thing as the normal cut off switch but with he inertia bit cut out of the loop and wired into th fuel pump wiring

On the Mondeo I've got anproper battery cut off with removable key fitted

I'm also looking at a way to rig up a spare central locking module to trip a switch somewhere