I wonder how long before they just put mandatory tracking chips in cars, rather than monkey patching it with expensive OCR machines on the road and in patrols vehicles.
EDIT: Apparently there already are, both in the US and elsewhere -- see below comments. Next time I'll Google this before posting, I promise! =D
In a related note, I can't cross US borders until the driving study is over; the border police are Not Amused at being recorded, and the researchers really discourage trying to cross a US border in the car that the gear is installed in.