Even simpler to hook the black box up to a GPS receiver that the car probably already has.
It also sounds pretty benign, even useful. But unlike Weires, I'm a technology guy -- and I have a very acute sense of how seemingly harmless new technologies have a tendency to metastasize into something far nastier and, usually, end up invading our privacy or diminishing our freedoms. And, perhaps due to my own driving history, the story of Weires and his black box had sirens going off in my head.
Think of the worst possible scenarios, and whatever you come up with has a good chance of happening. For example, you know those random checkpoint stops that the police set up every year around the holidays to catch drunks. I've never been a big fan of them, mostly for civil liberties reasons, but like most people I endure this little inconvenience for the perceived larger good.
But what about a checkpoint where the cop walks up, plugs his laptop into your car and then tickets you for going over the speed limit three times last week? Put up some "smart" speed signs that send out signals to your car's black box and it would be simple to make the comparison. Like that one?