Let the hive mind of Engadget get that for you.
"I am looking for a device that will stream sound from one source to several recipients. For example, I want to stream sound from my TV or stereo to my phone or MP3 player that has radio and Bluetooth capabilities. I have looked into radio transmitters and they seem like a decent choice, but I can't find one that uses external power (USB or from the plug) and I would want one with a transmit range of around 50 meters. Thanks!"
It was added to enhance the environment inside the stadium. I think it's a great addition and another good reason to go out and visit the Giants ballpark. By the way, they are still playing the ballgame right in front of you, so you still get to see the game live and in person.
It's a nice wow-factor, just like the giant Coke bottle. But I have mixed feelings about taking my kids to the ballpark where I know they'll get too distracted by giant Coke bottles and hi-def screens to notice the live game...