SikSync app for iPhone and iPad

All together now. SikSync allows you and your friends to easily syncronize your music – so that you can all (an unlimited number!) be listening to the same thing at the same time. Just bump your devices together and youre in sync. SikSync does not copy songs from one device to another; all devices must already have the app and the same song on them for SikSync to work.

Just load up the song in one device, start SikSync on the other device, wait for the second device to display "Ready to Bump", then bump them together to synchronize the song playback!