Your cellphone usage should be automatically linked to your car's GPS data and automatically bill you every time you use it while driving ? this is not that hard, I am sure the NSA already has all that data
Have you ever heard of this new thing called "passengers"? They're all the rage these days.
sorry I was a little sarcastic... but for passengers, they can always contest their tickets later... just like they have to do with red-light camera tickets.