I was wondering the other day how to relate secret information to different players in a game when they're all playing on the same TV. You can't put it on screen, because other players will be able to see it. You can't get around that by encoding it in a secret code known only to the player, either, because they don't have time to look it up.
Then I thought that you could put a separate headphone port in each controller, giving a private sound channel for each player. It satisfies all the requirements of secrecy, but it does require at least additions to the console hardware. And if we're talking about the Nintendo Wii here, the game would have to forego requiring any vigorous control motions or else headphones could be dislodged.
Mokalus of Borg
PS - I guess you could make the headphones wireless too.
PPS - Which means more batteries. Everything has a down side.