I developed a game for Windows Mobile. I am looking for a platform/SDK such that it will allow me sell extra levels and other in game items. There are SDKs for adding ads to the game (e.g. admob) but that is not what I am interested in. Basically I need a platform that will handle purchases for me. And they provide APIs that would allow me to direct user to appropriate payment application/website. Also I should be able to check what user have paid for already. Do you know any such platform that will work for Windows Mobile or Symbian? Thank you.
There seems to be a company called PlaySpan which does provide such functionality. I have no experience with them though.