bigtunacan

I've done a few indie games, but up until now they have all been single player games. For my next game I want to create a small asynchronous turn based game (something along the lines of Scrabble, Words With Friends, or Dominion). I know that the newest version of GameCenter supports something like this, but then it would be locked to only iOS; or at the very least I would have seperate code for each platform and someone on iPhone wouldn't be able to play someone else who is on Android or Facebook...

So I don't want to use GameCenter, instead I would rather an independent push server app I could use/purchase, or preferably just write my own. Since I'm new to this bit of it though I'm not sure where to start. I've googled a bunch but everything just points me back to GameCenter or something similar. Any advice would be greatly appreciated on this! Thanks.