I'm currently working on a multiplayer game. I've looked at a number of multiplayer services(player.io, playphone, gamespy, and others) but nothing really hits the mark. They are missing features, lack platform support or cost too much. What I'm looking for is a simple poor man's version of steam or xbox live. Not the game marketplace side of those two but the multiplayer services.

User accounts, profiles, presence info, friends, game stats, invites, on/offline messaging. Basically I'm looking for a unified multiplayer platform for all my games across devices.

Since I can't find what I'm planning to roll my own piece by piece. I plan to save on server resources by making most of the communication p2p. Things like game data and voice chat can be handled between peers and the server keeps track of user presence and only send updates when needed or requested. I know this runs the risk of cheating but that isn't a concern right now. I plan to run this on a Amazon ec2 micro server for development then move to a small to large instance when finished.

I figure user accounts would be the simplest to start with. Users can create accounts online or using in game dialog, login/out, change profile info. The user can access this info online or in game. I will need user authentication and secure communication between server and client. I figure all info will be stored in a database but I dont know how it can be stored securely and accessed from webserver and game services.

I would appreciate and links to tutorials, info or advice anyone could provide to get me started. Any programming language is fine but I plan to use c# on the server and c/c++ on devices. I would like to get started right away but I'm in no hurry to get it finished just yet. If you know of a service that already fits my requirements please let me know.