I offer this innovation free of charge to trustworthy state governments everywhere.
Many vehicles already sport GPS receivers. It would be a simple matter to program these to detect when a driver was exceding the speed limit. They indicate where you are, after all, and how fast you are going. All that is required is a slot in the dashboard next to the GPS for your credit card, and the penalty can be deducted from your account in real time! The money gathered could be used to subsidize the installation of such systems in all new cars.
The state troopers can then all put away their radar guns and go back to making the world safe for democracy, which they would all obviously prefer to be doing anyway.
More advanced vehicles could have their diagnostic systems wired, so that broken tail lights and the like could be penalized as well.
Suggested names for these cars:
The Chrysler Law Abiding Citizen
The Ford Conformist
The Chevy Piggy Bank
I can't wait for the future!