My friend has one of these, it beeps every time he brakes too hard... it's just a simple accelerometer. All for a discount. Hell no, I say. I drive pretty damn aggressively, but I'm always paying attention to driving... I have an excellent track record. These things should cross reference your phone usage and penalize people for being on the phone and/or texting while driving.
But there's also people who skim newspaper headlines, magazine articles while driving, or use their offline device like a Kindle or an iPod while driving who have similar increased chances of incidents, whose bad habits can't be tracked like that. Perhaps a study will find that parents with children in the car, or people who play music loudly, or someone with a family history of heart attacks, or any number of other things also increase the chance of accident, and if they track cellular usage, next they'll want to tackle whatever the next biggest offender is. Then pretty soon they'll just be videotaping the interior of your car and reading your medical records in a huge violation of your privacy.
You're right. I shouldn't really promote any additional ramping up of the surveillance state, it's already far too invasive.