Use your device together with that of your friends to make a single loudspeaker from which to spread your favorite music.
Prepare an event, select the song and the start time, and share via Bluetooth, or alternatively the event can be recreated on the individual devices.
Once you have set the event, will start a countdown, after which the music chosen will be played simultaneously on all devices.
If you're impressed by the GroupPlay application's advertising, but you can't afford to buy a Galaxy S4, then this is the app you wanted.
Are you ready for the next Flash mob?