Patently Apple:

Patent reveals yet another innovative concept that is designed to help users control their incoming calls and voicemail by simply swiping their finger over the external camera lens. It will control rewinding and fast forwarding voicemail. In addition, the new methodology will also enhance one handed navigation of web pages, documents, a contact list or your iTunes library by simply swiping the camera lens in different swiping motion combinations. In the future, the iPad may be able to take advantage of this feature if the camera is positioned correctly. This would theoretically allow a user to simply flick a finger over the camera lens to turn the page of a book or scroll a webpage without ever having to move your hand. This is an excellent idea on several fronts that will have Apple’s competition on the run, again.