I am very, very happy with my Viper 550ESP which appears to have been superceded with the Viper 560XV.
http://www.viper.com/security/...s.asp
It has been extremely reliable - not one glitch that I can remember - and the remote range is phenominal. I once started Q2 from the 16th floor of a hotel a half a block away from the building. I barely had visual contact with her.
I installed mine myself - but as Robert mentioned, don't try this at home unless you have a lot of time and are very comfortable with the work. I spent a week or so installing mine. It's buried so deep you'd never find it unless you're a very good thief. Everything is soldered and integrated into the existing wiring harnesses...
Heath