After installing the Pioneer Avic-Z2 Nav radio, I was petrified to leave my rig in any parking lot. So, I had a 2-way remote-start/alarm installed. It notifies the keyfob if there an intrusion. Well worth it (and makes that 357 useful)!

 

Best theft deterant is to never leave anything in plain view...ever...
In 30 years, the only time I have ever had a break in was when I left my radar detector atteched to the window at the mall.
Yep, right up front and busy as hell...
Since then, I do not leave any "low hanging fruit"....

There use to be a company that sold a motion detector, that set off a recording of a very mean dog barking...
I plan on getting one of those again!