The description isn't very detailed, so I'm going to assume that this app runs on several Macs, each with the same iTunes library. Then, it identifies where you are by checking for some Bluetooth-enabled object you're carrying such as a cellphone, and plays the exact same part of the music you were listening to on the next Mac that runs Music Follow Me as it detects said Bluetooth-enabled device.

Very cool concept, I hear Bill Gates's house does this. Would be cool if you copied him by hooking Macs running Music Follow Me up to speakers and used some kind of Bluetooth device to track you around, Bill Gates will hate you— but that's a good thing!