(this was originally posted on the Foundation forum a week or so ago, I repost it here for additional feedback and discussion)Consider an electronic ring that you wear on your finger. This ring can act as
an authenticator to devices that have cryptographic locks which makes it a natural complement for
smart property, but it can also be used for Bitcoin transactions as well.
Shops contain objects you want to buy, with theft prevented by using various kinds of alarm-triggering radio tags. With a key ring, the act of reaching out and taking an object from the shelf is enough to make your ring come into nearby contact with an NFC tag in the object itself - a brief flash is enough to tell you that the ring sent the product ID to your phone, which then communicated with the shop via its in-house wifi and successfully set up a payment. The payment wasn't broadcast yet, but at the door are powerful directional radios that can access the products NFC tags from a greater distance than what is normally possible. When they see the product leave the shop, your Bitcoin transaction is broadcast by the shop and the payment is locked in. If they see a product leave that has no corresponding payment, the alarm sounds.
Business deals have been sealed with a handshake for centuries. When two people wearing key rings handshake, their rings attest their identities to each other via NFC, and the rings then communicate that back to the users smartphones using Bluetooth. The wearers phone searches its inboxes and message histories looking for communication with the other person, and if it finds a price denominated in Bitcoins in a prior conversation that's used as the amount of money to transfer. Just agree in writing, and then when you meet a handshake seals the deal. As a bonus, it transparently exchanges keys that are also usable for encrypted communications.
Key Rings would give new meaning to wedding rituals. An exchange of rings would not only symbolise true love, but the act of putting on a wedding ring could also represent financial unity: my ring lets me spend your money, and your ring lets you spend mine. Receiving your first ring could be a coming-of-age rite.
The rings can be used to transparently release locks - by taking hold of a steering wheel, door handle or phone, the ring authenticates the wearer and the device starts up/opens/wakes up and logs you in. Rings could take the place of Oyster cards on the London Underground to conveniently pay for trips on public transport.
Finally, a key ring makes multi-party transactions physically natural. If three people have money in a set of 3-of-3 outputs, they can each put their hands on top of each other - the act of all rings being in proximity triggers the multi-signing process.