According to this CNN article, Canada is testing a system that uses GPS to determine your speed and the speed limit of your location to make it harder for you to exceed the speed limit. It does so by making it harder to depress the accellerator once you exceed the limit.
There are several things I don't like about this but the biggest is that it is a very small step from this to a system that automatically reports you if you are speeding. Then a small step from that to government tracking of your vehicle.
The article also mentions that these tests have been done already in parts of Europe. Any Europeans have more info about this? Is it being discussed much over there?