Information including:
1. Speed limit for the area/road I am in.
2. Real time radar report telling me how many cars/pedestrians e.t.c are around me.
3. Information on common accident types in the area I am driving in.
4. For my corner of the world, it will be good to get a report on road status before I take the route - something like gravel, cratered e.t.c
I suspect that something like this would sell like crazy for existing cars. Basically a thing were I install a camera/sensor that is hooked to such a device.