That seems like a great way to distribute some secret. Create an Arduino reader for the ring, save the secret in a format that requires 3 out of 5 rings to reconstruct and store them apart.

Only the most persistent and knowledgeable about the ring will go through the trouble to get the data off it.

That is the weirdest ebay listing I saw in a while. Also I want to have one super-badly now. Thank you :)

I remember the JavaONE when they were given. Oh getting old!

I think I still have one somewhere from that JavaOne.

What can you actually do with it?