Onkyo has announced the MHP-UW1 a wireless headphone system made up of headphones and a USB transmitter. You connect the USB transmitter to your PC's USB port and it operates as a bus-powered USB audio device. Audio is transmitted from the USB transmitter to the headphones via the 2.4GHz band.

Sales of the "MHP-UW1" 2.4GHz USB wireless headphones start late November - 10,000 yen.

News release:
http://www2.onkyo.com/jp/what/news.nsf/view/mhp_uw1