i look up when i hear an alarm because i know it could be mine, and even if it isnt, i know that i would want other people to pay attention to my alarm if it was going off in case somebody's tryin to do some shit.... my roomate just had his car hit and run in the parking lot at school and because somebody heard the alarm going off, they left him a note with the guys license plate number and all that crap and the dude got caught... so yeah. alarms are a good investment and people do get caught.
you should definitely get an interior pizo siren, they are straight baller and loud as shit. nobodys gonna fuck with your car with that going off right in their ear. and they can never get to them to cut them cuz you can hide em really well....
damnit, im giving away all of my secrets... i'd rather catch someone myself than let the police do it later...