I want to use Payvment to sell downloadable products via Facebook, however they don't off that option out of the box. They do, however, have an API found here: http://docs.payvment.com/display/publicdocs/Payvment+IPN+(Instant+Payvment+Notification)
What I want:
An automated implementation of the API so that purchasers on Facebook will receive an email automatically after purchase that provides a secure download link that will expire after seventy two hours. Files/script to be hosted on my own server space.