I think it would be far more useful for cars to have a black box, which could be accessed only via search warrant or court order. That way, you can be held responsible if your driving causes an accident.
I have a big problem with this.
In my opinion, it would violate the Third, Fourth, and Fifth Amendments.
The Fifth Amendment is obvious—one cannot be compelled to testify against one's self. By extension, I think one cannot be compelled to have one's own property equipped to testify against one's self either.
The Fourth is also obvious. Government doesn't get to put recording devices in our homes, even with the restriction that they need a warrant to access what is recorded. Government doesn't get to put such a device in our homes unless it first obtains a warrant. So why should our car be any different than our home in this respect?
So, how do I think this would violate the Third Amendment? I have a rather unusual view of what the Third Amendment is really about.
Ostensibly, what the Third Amendment prohibits is government compelling citizens to quarter soldiers (or government agents) in their own homes.
Now consider that when the Bill of Rights was invented, we had no electronics. No telephones, no sound recording devices, no radio, no microphone—nothing like that. If government wanted to eavesdrop on a private conversation, the only way to do so was to put a human being in a position to hear that conversation.
So what would be the purpose of government quartering its agents in private homes? It's not about housing; it's about putting those agents in a position to spy on the legitimate occupants of that home.
And what would be the purpose of government requiring such a “black box” device in a private automobile? It would be to spy on the owner or operator of that automobile.