Poster: Really sorry to hear about your loss.
Vaqas1: i salute you. inshALLAH i would do the same if i am in similar situation.
Now coming to the anti-car theft techniques.
Here is a fun idea
I am actually interested in this stuff for other fun purposes than car theft
idea is to get a led panel installed on ur rear screen (perfect if it's transparent), and a computer which can control the text displayed on led panel
instead of a computer you can also make a small controller with few buttons with feeded lines like "Chor ha is gari me", "Sorry, i am in hurry!"
Chor wala message by default pre-selected hona chahiye whenever you turn on your car now imagine how it will be .. haha
another idea is to do something with number plates.. e.g. a sliding led panel on number plate to display alerts/texts/ ... and few hidden buttons in your car to control it...
imagine what would happen if you successfully and perfectly accomplish something like this. i am sure police at checkposts and public will get lots of attention and they might stop the car. and chor bechara would be like ... wtf....
P.S. using this idea you can also display your cellfone number to an interested lady driving right behind your car