The Nintendo Fan Network is an app for Nintendo DSi and 3DS that allows fans at Safeco Field (home of the Seattle Mariners) to play minigames, track stats in real-time, and even order food delivered to their seats.
My friends and I got to vote pictures we took of each other with our 3DSes onto the megatron at Safeco Field. And I think we could see strike zone data for each at-bat too, long before they were making that nearly as available on the big screen? Shame it's retired now. 10/10