This would be kind of big, but I think would be worth it.
A new message type sent to players by game owners. Of course only after they accept to be sent messages. I was thinking this could function a lot like mobile notifications. With the exception, to not be abused a limit on how many can be sent to the players.
I could use this for a trivia game(Similar to Triva Crack) which would send you notifications when you have a game, or its your turn.
This could also be used to notify users of updates, or changes to the game. Which could work kind of like a news letter.