Black boxes of a sort have been in cars for years, they record pretty minimal data. Reading "black box" recordings of accidents can be chilling. I've read event recordings of fatality accidents from the ABS and SRS systems and you get much useful information. Speed, seatbelt status, brake activity, speed of deceleration, airbag timing and deployment etc. You can read the data and see how an accident played out for a car with almost nothing else. You can see when someone hit the brake, what if any ABS events triggered, seatbelt ratchet (tells you someone hit the brakes hard enough to not only trigger a wheel to skid but to slam occupants into their seatbelts causing them to lock). By airbag timing and deployment you can see where the car hit first and which direction it hit, spun and hit again etc all by deployment sequence.
I also read a case where someone tried to sue GM for faulty ABS that had never gone off in their car although they were an extremely careful driver etc. GM subpoena'd the ABS box and discovered over 500 events in only a few thousand miles of driving...
As long as gps logging isn't occurring and 4th amendment is observed I don't see a problem.