The biggest problem with this is going to be the iPhone-style inconvenience of lining one's head up properly to unlock a door. When the technology gets streamli

The biggest problem with this is going to be the iPhone-style inconvenience of lining one's head up properly to unlock a door. When the technology gets streamlined and unobtrusive it will be adopted by everyone but career criminals and severe paranoids. Ease of use is the issue, if the new system takes more work and is a pain in the ass people are going to dislike it and complain about 'privacy' because that's the popular topic.