Face Detection API in iOS 5.

CoreImage framework introduced in iOS 5 API has  classes called CIFaceFeature  and CIDetector.This class has potentially has been added for detecting face feature in the image. Currently, it offers following functionalities:

•   hasLeftEyePosition 
•   hasRightEyePosition 
•   hasMouthPosition 
•   leftEyePosition 
•   rightEyePosition 
•   mouthPosition 

CIDetector has ability to detect face as a whole.

If you are wondering how to add framework in your project, refer to this post. LINK