I'd go with a 2-way pager Viper Alarm System. It'll show you a diagram of the car and has triggers on the doors, trunk lid, and hood and it's rather difficult for thieves/carjackers to disarm the system before authorities are contacted. It's a relatively cheap alarm system, considering the technology it provides.
I plan on eventually getting one installed in my Stealth and it seems a bunch of fellow 3000GT VR-4/Stealth R/T Twin-Turbo owners swear by them. It's also a good idea to have a fuel cut-off switch along with an electrical cut-off just to make sure your car is almost 100% protected with all these tangents covered.