Apparently advanced windshield cameras have been for sale in the USA for months. Even though I saw my first ad last week, there are on-line reviews from happy customers dating back to September 2012. Some come with a shock sensor (I guess to mark the accident and prevent overwriting the data). They also offer special panoramic view (not fish eye) cameras to avoid image distortion as well as the impressive WDR contrast control. Maybe they'll also offer a version to catch rural mailbox vandals!
I've read of quite a few cases where US citizens were arrested for audio and/or video recording while being stopped by a police officer. (Arrests subsequently thrown out by wiser judges.) Wonder what the upshot will be if these things are discreetly mounted?