To be able to match two images and unlock features in the phone for security purposes. An example of this would be a consumer takes a picture of him or herself and is stored in the phone as the default picture. Certain files and passwords are locked in this app. These apps can only be unlocked if the picture they take (at the time they want to unlock the app) matches the default picture they took initially. There are two features of this app.
1) to have the app match a face from a picture that is being taken, with the picture of themselves that is stored in the phone.
2) having the feature of filling forms automatically and password field when using an Internet Browser as well when image match is positive.
3) storing/locking files and passwords until image match happens
This may be similar to face recognition but I do not think it has to go to that extent. If the algorithm can validate that the images are of the same person, that is all that would be required to activate/unlock the private apps.
This site may provide additional information for the source code for face recognition however it may not need to be as elaborate: Source Code: http://www.face-rec.org/source-codes/
There is this SDK http://www.neurotechnology.com/vl_sdk.html, and we can use already available SDK kits that match.