It can become something like PokerChess
The first player make an offer, example:
- Start a match with 100 bitcoin in the play-wallet. ( the servive must have a wallet with all bitcoin, and another wallet to start matches, the play-wallet )
The offer go to a list with all offers of all players on the service.
If the other player wants to play, he must have the same amount of bitcoin in his play-wallet.
If 2 players went to the agreement about the match ( about the rules and play-wallet amount ), then it starts.
Now, during the game both players can make an higher bet after every move.
If someone makes an higher bet, the other one must make the same bet or higher to be able to continue the game.
( if the game has a timer, it must stop if one of the 2 players makes a new bet )
Everyone can leave the game when ever they want, but they will lose all their past bets.
The service must have all kinds of statistics about all players.
It can be possible also to open ( or not ) the match to spectators, so that they can also bet between each other.