There appears to be some code on github[0]. I haven't looked through it yet though
170 karma · joined April 12, 2012
There are many ways for this to be achieved eg: username/password, Oauth, some form of secret key.
I don't think we can completely get rid of a login mechanism completely, but it may be possible to hide this from the user.
Face or speech recognition could be used, but I don't really like that idea. I guess a chip/rfid tag could be implanted into the body, but somehow I don't think most people would want to be identified in this way.