This is a cool idea.

I've actually given this idea much thought. I want to create a currency that would serve as a sort of identification system in which it would serve as evidence that someone belonged to a certain group. I'm not sure how it could be done, but it would have to have certain characteristics like:

-Each coin would have to be indivisible
-Each coin would have to have its own serial number
-it would have to be capable have to be capable of restricting transference of coins like maybe 2 transfers.
-must be able to be assigned a public/private key pair and/or a passphrase. At the time of transfer.

The idea is that an organization could purchase a number of these coins and transfer them to members of the organization. Those members could then show evidence of membership by producing the serial number and the passphrase. It wouldn't be true authentication, but could potentially be tied to physical coins displaying the organization's emblem along with the serial number.

PS

please don't steal my idea and become rich. I'll feel really stupid, unless you come to me and give me a bitcoin or two.