Besides the fact that you could get jacked for this if you walk through our Dojo at night, the Soundwalk speaker harness looks like exactly the gear for any true urban-sherpa type. You can click the link if you want all the technical details and whatnot, but basically this piece has speakers in it so you can bump your tunes from your favorite DAP. I guess ideally you would rock this underneath your gi. I hope it got a mute button for stealth mode.

The Soundwalk Speaker Harness
Or read the source article at Red Ferret