I have a Viper GPS alarm in my NSX. The alarm has a battery backup good for days. The car calls up to 4 devices. Mine calls my cell phone, home phone, pager and email. I can track the car with a laptop computer in realtime. If the car is moved and the alarm is not tripped, the car calls to tell me it is out of its parked zone. I can kill the ignition, remotely, open the trunk, doors or test the alarm through my cell phone. If my main battery is low, I get a call. I can even put a speed warning notification on the car. The unit costs about $8 per month. My wife loves it when my car calls my phone to check in. Got to love technology. Jerry