GNU Taler Wallet by Florian Dold, sebasjm

GNU Taler - Taxable Anonymous Libre Electronic Reserves

Note: The add-on is still experimental and intended for developers.
Check out the demonstration.

Taxable
Unlike Bitcoin or cash payments, Taler ensures that governments can easily track their citizen's income and thus collect sales, value-added or income taxes. Taler is thus a currency for the mainstream economy, and not the black market.

Anonymous
When you pay with Taler, your identity does not have to be revealed to the merchant. The bank, government and mint will also never learn how you spent your electronic money. However, you can prove that you paid in court if necessary.

Libre
Taler is free software from GNU implementing an open protocol. Anybody is welcome to inspect our code and integrate our reference implementation into their applications.

Electronic
Taler is designed to work on the Internet. Using a so-called RESTful protocol over HTTP or HTTPS, Taler is easy to integrate with existing Web applications.

Reserves
Taler uses an electronic mint holding financial reserves in existing currencies. This means that Taler is not a new currency with the inherent currency fluctuation risks, but instead the cryptographic coins correspond to existing currencies, such as US Dollars, Euros or even BitCoins.

Read more at taler.net