A great addition to this would be if everything was synched from a central server.
20 commuters pressing their toes down and letting out a sigh at the same time.
It would be like a multiplayer protest against attention-grabbing phones. Everybody playing the game would know if someone else was playing the game, but no one else.
It may defeat the original purpose of the game to blend in, but I think it could be pretty fun to observe something like that.
