Progressive Insurance is now offering "pay as you drive" or PAYD insurance. Progressive will put a little tag on your car and it knows how often you drive - which, in combination with your safe driving record - determines your premium. Here are some potential benefits from our friends at Wikipedia:
- Commercial benefits to the insurance company from better alignment of insurance with actual risk. Improved customer segmentation.
- Potential cost-savings for responsible customers.
- Social and environmental benefits from more responsible and less unnecessary driving.
- Due to the 24/7 aspects of vehicle location, it enhances security - both personal security and vehicle security. The GPS technology could be used to trace the vehicle whereabouts following an accident, breakdown or theft. 
- More choice for consumers on the type of car insurance available to buy.
- The same GPS technology can often be used to provide other (non insurance) benefits to consumers,e.g. satellite navigation 
- Social benefits from accessibility to affordable insurance for young drivers - rather than paying for irresponsible peers, with this type of insurance young drivers pay for how they drive.
So what other behavior changing ideas are out there?