Discussion is ongoing at Unc's joint on the latest Authorized User or "Smart Gun" concept out of Deutschland.
The problem with the whole "Smart Gun" concept is that it is derived from an incorrect view of weapons. If you look at firearms as a type of sporting goods, then there's nothing particularly wrong with Authorized User technology. If it fails or malfunctions, it's no big deal in the grand scheme of things; you miss your duck or deer or clay pigeon or paper bullseye, and your afternoon or weekend is ruined, but hey, that's the price of safety.
But if you look at a firearm as a piece of emergency equipment, then Authorized User technology is a no-go. A cop's partner may need to use her gun; my roommate may need to use mine. It needs to work right the first time, every time. It cannot malfunction or, if it does so, it must "fail-dangerous", in such a way as to leave me the ability to use the gun to defend myself, even if the Authorized User function no longer works.
Look at it this way: Would you put fingerprint recognition sensors on a fire extinguisher? How about a biometric sensor on a reserve parachute? No, you wouldn't, because it needs to be as easy as possible for anybody to operate, even under duress and in harsh environmental conditions.