New tweak in Cydia, RecognizeMe, is the first ever facial recognition for IOS. Recognize me works with all IOS 4.x+ and sits on the pass code lock screen. RecognizeMe uses the front facing camera on the iPhone 4, iPod Touch 4 and iPad 2 once a jailbreak is released. It is configurable using the settings.app. $6.99 on Cydia. Search for it.