i can't afford to install an alarm/immobiliser in my car but would like to do something to safeguard my pride and joy.

i was thinking of installing a switch hidden in the cabin, to something important in the engine bay..... perhaps the fuel pump or something.

but i have no idea if the fuel pump is electrically or mechanically driven etc. in fact i don't even know where it is....
so has anyone got any good suggestions as to what might be my best and easiest DIY immobiliser?

thanks in advance as always.