My name is Andreas Petersson. I am the business developer at Mycelium.
We offer the Mycelium Wallet - the fastest and best Bitcoin Wallet. We are also the developers of the Bitcoincard (see bitcoincard.org) which is not released yet. We already support importing private keys and addresses (pubkeys). There is also a "cold storage spending wizard" that could be adapted to specifically support NFC ring.
You can try out how it works using any paper wallet.
The wallet is not in version 1.0 yet so it is labeled as "beta", and it is not actively promoted so far, yet we still have a userbase of thousands of users.
I think your NFC ring could be a nice complement to our software, because of our system architecture we are the only mobile wallet that allows seamless import of private keys.
you can find the wallet at
[b:3v3yi9qv]Please get in direct contact with me to discuss a cooperation.[/b:3v3yi9qv] You can get in contact with me on skype (andreas_petersson) or via email at firstname.lastname@example.org
or if you prefer our landline phone number, it is posted on