Patently Apple has a report on Apple's
latest just-revealed patent application for a system that runs on iOS devices that would recognize user faces and their local presence (originally filed in Q2 of 2010, released by the USPTO this week). It sounds like the old Minority Report gag, where your iOS device would monitor its surrounding environment for faces, and when one gets close enough and is identified as yours, the device would unlock and open up for use. Apple's patent also mentions algorithms for identifying specific features of the face, such as the eyes and the tip of the nose, and even methods to deal with low-light situations and other criteria which would make it hard to do the identification.
Update: Yes, as commenters and other sites point out, the Galaxy Nexus and other Android 4.0 Ice Cream Sandwich phones (if you can find any) include a Face Unlock feature. They were introduced this fall; Apple's patent application is from 18 months ago. Whether Apple's patent will be granted or not, and whether that impacts Google's feature, is yet to be seen.
Sounds like fascinating stuff. Of course, you might worry about security while doing something like this (could it be fooled with a picture, do you think?), but then again, iOS already offers different levels of security -- some people don't use the unlock code at all on their devices anyway. And a system like this would be more than just a handy login feature -- the software also could be used to display personal information, check a person's mood, or even figure out whether the user is paying attention for not. Those stats, specifically, would probably make for very interesting reading for any developers out there.
As with all Apple patents, this just shows what they're kicking around at Cupertino, not actual technology we'll be guaranteed to see on any devices in the future. But it would be cool -- hopefully Apple will work this kind of thing out, and maybe in iOS 7, we'll see faces put to a whole new use.