As I mentioned elsewhere, laws vary state-to-stae on who has to be aware of recording for it to be legal. I've never considered how that applies to dashboard cameras. I suspect that what law exists specifies audio recording, with no mention of video. If that's the case, it's bad law, IMO.
So does anyone know: In the states where it's illegal to record your own phone conversations without informing the other party, are the police allowed to record audio or video of you without your consent?