Thought I'd point to the excellent Carcom car intelligence system, also by Intelematics (the crew behind SUNA Traffic Channel), in case you'd never heard of it. First launched a couple of years ago, it was so well received that the company went into heavy duty production for factory fitting these systems for a number of automakers. If you have Holden Assist, Toyota Link, or Mitsubishi Diamondtrack, then you have the Carcom system. For everyone else, you can buy direct for around $2000 installation and $300 per year.Carcom is awesome not because it is some kind of car tracking security system. But it is one of those. It's the 'full service' style intelligence of the package that wins me over. You get all kinds of notifications to your mobile via SMS if you want, like a low battery warning. Lock they keys in? Phone Carcom and they'll remote unlock it for you. Have a scary incident out on the road? Hit the SOS and you have two-way communication with a Carcom operator within the car, and they know exactly where you are to send the police. It ties in with your roadside assistance service too, so they know exactly where you are if you break down.
And this has to be the sexiest security system ever. Geolocking! No such thing as an override - if your car moves from the position you parked it in, you will get an SMS to tell you it is on the move. If you're in it, no drama (unless you're in the boot). If you're not, call them and the police will be on it in no time.
For the price, it's a pretty good investment if you have a better than average car, or you want to improve your personal safety out on the road. If you are the one dishing out the roadrage, this probably isn't up your alley.