In some parts of Denmark you can get a reduced insurrance if you allow the insurrance company to install a GPS unit in your car and they can see that you respect the speed limits. Because most streets are charted they can see if you are speeding. My car is owned by the firm I am working for so such a device is not installed in my car due to security reasons.
Alcohol interlocs are now installed in most busses carrying passengers on regular schedule. They are voluntary in Sweden if you have not been convicted of DUI, but mandatory after the first conviction.
I don't know if the insurrance companies have started the use of GPS in return for lower fees anywhere in the States, but it could be worth to investigate that. If the driver knows that someone is watching him he would be less motivated to drive too fast.
