Woow, sounds awsome!
In the video they talk about Bitcoin, saying it can store your wallet address to receive payment. Wouldn't it be fantastic if it could store your private key too, thus being able to make payments as well?
Ya that part of was the coolest part. Yeah I agree about storing your private key.
That might be quite risky for anything but smallest amount of coins, since the private key would be readable for anyone getting close enough. Think about using this in a store: you would have to trust cashier withdrawing right sum.
And where would the change go, back to a new key generated by the cashier machine? What if NFC link is interrupted while writing the new key to the ring, would the BTC be lost?
Yes, true. I believe he mentioned another way around that even.