Hmmm.... Sounds like Camera Strobe triggered to a motion or capacitive touch sensor around the Stereo might be a cheap solution to run em off... A few successive "pops" of a white Strobe in their faces [only when the Ignition is off] might fake em/disorient them into giving up on the job, especially if a fake window decal said "Protected By Wireless Webcam".

Just a "premptive" Techno thought, since it's rare to be around w/Firearms in hand to deliver Western Justice to the jerks.

As seen on TV several weeks ago, the new idea seems to be acid-etching the VIN on all the vehicle windows. This dissuades theft up front and vehicle sales to chop shops, since shops don't want to screw with replacing all the glass to hide the stolen vehicle VIN. On an SUV with such etched windows, a fake "Wireless Webcam" sticker might be taken more seriously, since alarms are all kinda "mind games" anyway.

Of course, an insulated Stereo front panel fascia and some serious interlocks [so as to not hurt the Owner] that hit a Thief with ~50,000 volts or so momentarily would be another "stealth" Techno solution. Couple your alarm trigger to your wireless unit or Pager and go outside in time to watch the jerk froth at the mouth on the ground by your Monty...

A nice, close-up shot of Mace, etc., "auto-delivered" by Solenoid from a small hole around the Stereo is another thought... A 30 second delay after break-in to trigger the Mace spray should be about right... Just interlock it well to avoid mishaps.