It's not much more of a stretch than what currently is able to be done/is done.
I mean, my phone bypasses the lock screen if I press the power button and it sees my face. A lot of the features they describe are for when the phone is on anyway.
And when it's off it'd just see the insides of my pocket mostly
![Cheesy :D](http://www.tekforums.net/Smileys/teksmileys/cheesy.gif)
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