FaceBlimp on iTunes store for iPhone, iPad and iPod Touch (requires iOS 5 or newer).
Just releases this app that utilizes iOS 5′s new face detection capability. The app detects the eyes and mouth in the picture them animates them. Apply glasses and mustache to the face using easy to use interface. Save the photo into photo ablum or send via email. You cam import photos or take photos using the device camera.
More about iOS 5 facial detection can be read here: http://www.permadi.com/blog/2011/12/facial-recognition-in-ios-5/