Yanko Design has some interesting concept gadgets, like the “Information Ring”.
The idea is that you wear this ring on a finger, the ring operates something on the order of an RFID type device which contains some information about you, let’s say an equivalent of your business card.
When you shake hands with someone else that is wearing an Information Ring, the two rings sense each other’s proximity and exchange information about each user then store this other user’s data in its own ring. This is a great idea for people that travel a lot and make many business contacts or social aquaintences.
There is a card associated with each ring as well, this card is about the size and shape of an identification card. It downloads information from your ring allowing you to sift or browse through the contacts you’ve made.
The power source for the ring is provided by the wearer’s body temperature, so it doesn’t need any external interfaces.
I didn’t see any way to purchase these rings so I’m assuming for now it’s a concept device. Please holler if you glean any more information than above.