I use a DEI / Viper
You can change alot of stuff like; chirp on off, pager beep on off, pager vibrate on off, shock sensitivity from the pager, etc.
I hear good stuff about compustars, but you can get a DEI installed for less than $400 with some cool options. The setup I use has the proximity sensor wired into my window motors

. If I have my windows down and someone gets to close the windows roll themselves up.