Facebook has announced the launch of a new feature for the third party app developers.
Developers offering Facebook Apps now have access to In-App Currency Offers.
Facebook spoke about this new feature:
Today we’re launching in-app currency offers, which lets developers award users with their own in-app currency (e.g., Fred Currency in Fred’s game) upon completing an offer.
Previously, developers were able to integrate Credits offers, where users earned Facebook Credits by completing offers. The new in-app currency offers product is in addition to the Credits offers product, and you can utilize either or both in your app.