Microsoft Research has released three different Face manipulation apps in Windows Phone Marketplace so far. Face Mask, Face Touch and Face Swap are the apps you can now find it in marketplace. Now, Microsoft Research has released an SDK that developers can use to process Face images, etc,.
The Microsoft Face SDK provides many state-of-the-art algorithms to process face images, such as face detection, alignment, tracking, and cartooning. The SDK makes it easy for developers to create interesting, face-related Windows Phone applications.
I expect some cool apps from Windows Phone developers using this SDK. Download the SDK here.