The dominant media player of the '00s (the iPod) still hasn't integrated with wireless headphones. Maybe it should take a quick lesson from the dominant media player of the '80s: the Walkman.
This 1988 WM-505 (which may not even have made it to the US) was dug up by retrothing, and comes both with wireless headphone ability and a rechargeable (?) proprietary Sony slim battery. The whole thing is pretty damn small for a Walkman from 1988, and is impressive for both its early wireless-ness, and for the engineering acumen needed to make something so compact. [Retro thing via Crunchgear]