Apple have stated that developers won't have access to the fingerprint scanner. I can understand that they want to limit the access of the fingerprint for security reasons. Several apps have passwords like Facebook, 1password, Dropbox etc.. The fingerprint scanner wold be really useful in those situations. An easy solution would be to having ICloud keychain store password for apps, just like websites. A touch with your finger and you can access Facebook, 1password, mail, Dropbox, banking apps etc. I would find very useful, since I use 1password a lot. An easy solution and the developers won't have access to the fingerprint scanner.