I just wanted to be able to listen to music with my brothers, which both have Lumia 920s, and walk down the street with all of them playing the same song.
You can do it manually though, by making a playlist and starting them at the same time. Kinda cool, the effects of the music coming from multiple devices makes it sound really good.
i couldn't remember app name either until i checked my firefox bookmarkshaha I was going crazy trying to find this video. I knew there was an app I just couldn't find it!