Here’s a pretty cool MP3 player design concept called the “Plug and Player” that combines the audio player with the plug itself (I believe that’s a European style plug). With iPod-like devices being shrunk down to small sizes, this concept is entirely feasible. Granted you probably don’t two little prongs sticking into your pocket and playing it while it’s plugged in just seems a bit awkward.
Of course similar devices that had an integrated USB port have been around for a while (the earlier gumstick style iPod Shuffles did) but as an exercise in minimalist design, this works.
Single Flare Clear Opalite Moonstone Ear Plugs and Tunnels with O-Ring Stretcher Expander Pair (00g(10mm))