I rolled my own solution to this for a mobile turn-based game I have in development. Most of the time, the device is just polling to see whether there's anything that needs updating. As part of my polling query I pass a signature of the current game state (game-round, with a few other bits). On the server, if that checks out, then the reply is tiny. If there's the need for an update, I send back what's changed and update my views on the client-side. It's definitely not the right solution for every scenario, but I've found it works well for my specific situation.