By comparison with the earlier $18 Ozaki iCommand Controller for iPod shuffle 3G, Belkin’s Headphone Adapter is a more attractive but also physically larger accessory. Both devices incorporate the same three buttons—volume up, volume down, and multi-function play/pause/track change—found on Apple’s most recent Earphones and In-Ear Headphones with Remote and Mic, but they do it in different ways: Ozaki adds the buttons…