“Our top priority always has been to build technology to support our clubs and fans with an unrivaled experience in these world-class facilities,” Adam Ritter, SVP, Wireless, MLBAM, said in a statement. “The introduction of iBeacon services in our At The Ballpark app will be the latest evolution in this process, giving us another important platform to engage fans with their surroundings and to enjoy customized experiences through their iPhones.”
Apple's iBeacon technology uses Bluetooth Low Energy (LE) to communicate with receptive devices that are quite near and push information to those devices. Though it would be ideal for directing people to their seats, Major League Baseball appears to be using them more for information and marketing.
The league is being coy with precisely what info will be pushed to users, Re/code noted that a demonstration of the technology earlier in the year included playing a video for users and sending them coupons when they got near a stadium store.
An update to the app linked above will be released on opening day—you know, because that way people have to mess with it at the last minute, if they remember—that is iBeacon-aware. The season starts in March.