Car alarms are always good to have, but I'd never depend on one. The idea behind car alarms back in the day was that the alarm would go off and passers-by would be like "oh my! that car is being broken into! let's call the police!" but now they are so commonplace that it's "dammit, if that stupid alarm doesn't stop waking me up i'm gonna go tear it out myself!". hehe. I'd still put one in, but I'd also add a lojack or GPS locator system. I'm getting an Omega ATV-1000s security system with GPS locator so when someone jacks my truck I can go to a website and find out where it's at. You can even set it so if it goes over a certain speed for a certain time it'll email you. Pretty sweet, hehe. The alarm itself is $65 and the GPS module is $385.