Engadget have got a hands-on gallery with the RCA Jet Stream cordless earphones, which are based on the Kleer reference design SlashGear wrote lustfully about last year. With a five to six foot range, using proprietary RF connectivity with apparently incredible audio quality, as demonstrated they're working with a specific RCA mp3 player but there's no reason why future PMPs could have the hardwear built-in, or even a plug-in dongle for a retrofit solution.
The most surprising thing, perhaps, is the $129 price-tag. Vincent, you hear me? Bring me back a set of these!
Hands-on with the RCA Jet Stream [Engadget]