The new screen lock feature Ice Cream Sandwich has (face unlock) seemed so awesome when Google & Samsung unveiled the Galaxy Nexus one month ago. Basically, face unlock does what it actually says : uses your face to unlock the phone so you can use it, obviously. But not by slamming your face on the phone'ss screen; you take a photo of yourself, and then, every time you want to unlock the phone, the frontal camera will be used to detect your face and... well, it should be pretty straightforward.
As secure as this feature might sound to you, it is NOT 100% hack-proof (so-to-say), and the video below demonstrates just that.
Basically, if you take a photo of the person whose face has been used to secure the phone and put that in the viewfinder... voila! Phone unlocked! But the photo has to be pretty good : you won't be able to use your girlfriend's face from a photo you taken at a party or something... it has to be like a photo for an ID card or a passport, obviously -- so it'll look very much alike the original photo (or we should call it a face this time).
So, if your boss leaves his Android 4.0-powered device in his office and you happen to find it... make sure you have a very high-detail photo of his face in your phone. "Hey boss, let me photograph your face; just so I can use it in the future in case you lose your phone, haha".