I've got one of these hidden in a secret location - foolproof (unless the fool has a short length of wire to bypass it if they can find it, or intends nicking it by towing it away)
Dint stop em breaking the windows and nicking stuff out of it - i moved to a quiet part of a small cornish town for that, which helps a bit!
pet snake is wot yer need. just leave it basking in the sun on top of the dash board. not many folk will go near it, course it has its draw backs in cold weather as they tend to seek out warm places like around the heater pipes or under the seat.