There are many solutions for controlling music on a phone with your headphones. Conventional wisdom has long produced in-line remotes, traditionally on the right wire of the headphones, to provide some sort of control — be that a single button for toggling play / pause or a more advanced three-button setup that adds volume control and even a microphone. Apple once tried to make an iPod Shuffle entirely based on headphone controls, but it gave up on that pretty quickly.
