How do firemen patch a hole in a fire hose while they are fighting a fire and they can't shut off the hydrant?
I have installed hundreds of car alarms and remote start/alarms. There are alot of brands out there. I would suggest buying one that has a lifetime warranty on parts and labor from a reputable place that will install it for you. The brands I would recommend are: Anything from DEI (viper, hornet, clifford, python) AST Scosche Avoid bulldog (wal-mart) security systems.
If I had a room mate period, I would probably wake them up.