Check out the prototype for Choice Chamber, an action game that allows one player to control the main character while infinite other players in real time influence how the game evolves. The main player streams his or her game to twitch.tv, while the chat participates in a constant series of polls that affect how the game changes, from power-ups to enemy spawns.
Choice Chamber is a side-scrolling action game that allows one player to control the main character, guiding him/her through a barrage of enemies, environmental hazards, and likely other dangers.
The rest of the infinite players are watching this game be played live, while constantly giving feedback to help shape the outcome of the game in real time.
This is all done through twitch.tv. Other than a player needing the game to play, the rest of the players watching don’t need any additional software or login outside of being able to chat in a regular twitch chat room.