Whatever Headphones you use (as opposed to a Headset) you do not need a wire
out of the Xbox to the Headphones. We wanted to make sure that while you were 
getting a great headphone experience you were still able to get up and walk 
around. What constitutes "wireless" headphones, in our view, is that there is 
no physical cable running from the console to the headphones. 

But to provide the most reliability without breaking the bank, we needed to 
stick with the Microsoft concept of a short, physical connection between the
controller and the X2 headphones. We could have incorporated a Bluetooth
sender and receiver pair in an adapter for the controller, and put a Bluetooth
receiver in the headset. 
 
But right now, Bluetooth headphones alone (without the sender) cost more than
the X2. In addition, we wanted to make sure that we didn't introduce delay or
interference issues. For us, the best game experience is with the integration
of game audio with XBL chat, and the freedom of movement that the 360's
wireless controller gives you in the first place.
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