Just a random thought that occurred - do you think you could use the ring as a friend unlock for a social 'Ring' network?
I'm thinking of a social network that you only 'friend' by effectively authenticating them on your device. That way you'd have a fairly tight network of only people you know or have actually met. One of the advantages of something like this would be that it could be used for a younger social network (10+ years) where you'd have some assurance that kids would not get contacted by outsiders or people not actually met.
The whole 'ring' ethos then pretty much sells itself, I suppose you could expand to other jewelry too with an embedded identity.