I wrote it before ( check archives about theft issues ) and i write it again :

--- All of what you do is useless, because FIRST the thief takes the unit away, THEN everything smart that you think of comes into action, still annoying for the thief, but totally useless for you, the unit is away, the damage is there.


Forget it.
Take it out when leaving the car.

Thats all.


Nils

The only effort which is worth a try is the following :

Put a sticker or label on the unit that says something like this:


"Dear thief, this car stereo is very important to me, so do not hesitate to contact me after you got it, Then we can think about a way to get it back to me, and you will be rewarded with no less then $500, maybe just send me an E-Mail to XXXX, using an anonymous E-Mail account like Hotmail.
This way you are not in danger of getting caught and we can talk about things ...
Thanks, i was stupid enough to leave it in the car, now lets make a deal ! "


Or similar.
Only chance.

Nils, whose car(s) were raped 13 times by now, because of stupidity, bad luck and relying on so called "prevention systems" .