Google Patents Facial Recognition For Android Security
It's true that a similar technology already exists in Android 4.1/4.2 Jelly Bean, which has users blink to unlock the device. The problem there is that it's relatively easy to thwart by taking an image of the device's owner, painting over the eyes in Photoshop with the same color as their surrounding skin, and then flashing the two photos to simulate a blink (we're not condoning this behavior, but it's a well known hack and one of the reasons why Google is still working to improve facial recognition).
The technology Google is trying to patent is a little different. It uses a two-part authentication system, the first being the recognition of at least one facial feature, such as that of an eye, eyebrow, the mouth area, forehead, or noise. Secondly, it looks for a gesture. You could be frowning, wrinkling your nose, or sticking out your tongue, to name a few possible examples.

What about tricking the device? Google explains some of the anti-spoofing methods that might be included.
Google also describes emitting a low light beam at either captured image to help detect whether or not the camera is looking at a real person or a photograph that someone is holding up.
Not all patents come to fruition, but given Google's past attempts at integrating face recognition technology into Android, we wouldn't be surprised if these methods found their way into Key Lime Pie.