I dont know if you have this already but really dark tinted windows work well. Its a little odd to see someones face pressed against your window just to see whats inside If you see that, that persons got some balls. I would think that if people saw that it would get there attention, alot more attention then a alarm blareing IMO??

I have 5% tint (yes illegal) but before that i use to take off the face on my headunit, now i dont. Plus i have 2 alarms, i got the factory for starter kill and if doors, trunk, or hood is opened and a cheap alarm for broken windows.

Also just a tip try not to play the stereo loud in neigborhoods, i always turn my stereo down in neighborhoods, at lights and some parts or FL that im not use to driving in