I like the idea but the problem is it is only using the phone as a viewfinder. Once you take a picture it'll be on a micro SD card on the lens attachment, there will be no way to send it via the phone to FaceBook etc. I doubt if the pictures will be GPS tagged like a normal iPhone photo and many of the other options will be limited.
For the same price you can buy a good compact camera.
I wish that Apple would do an iOS version of the Galaxy camera.