Incoming Calls Foto Diary @ iOS

Hi! I am curious about this website service, and thought I'll try it out with an old idea from me. At each incoming accepted phonecall, the iphone takes a picture from what the camera sees at that moment. Optionally the user image from the caller is superimposed in a corner. The picture will be saved lowres. I expect this only to be possible with jailbreaked iPhones, so no need for official Apple licensing.