In my old mustang gt vert I had a sensor that would detect movement in the car. If the top was down with the alarmed armed, waving your hands inside the car would trigger the alarm.
Not sure how useful that is in a sedan but it was great in convertible.

 

Thats the alarm I had on my previous car due to my system needing protection. The GS...well i Just never bothered. It was a clifford, and used a motion detector for outside the car, and another one for inside thecar. Warning for the outside, and the second there was movement inside, the alarm went off.
When i get rid of this car, I can say the next one will probably have an alarm installed similar to that.

 

if I mod my GS the first thing I am going to do it upgrade the factory alarm with a real alarm. I had a derringer II, I think.

 

Maybe you pissed off someone. I remember one time I accidentally cut someone off for a parking spot and started to go into a store. My friend noticed that this car I cut off circled around. This guy looked like he just got out of jail. I apologized to the guy and went on my way. Next time look around to see if you might have accidentally pissed someone off. :eek:

 

I can see keying a car but breaking into a car for a traffic altercation is a little extreme. Maybe, he stole someone else's girl?