Why aren't there any Bluetooth USB cable replacements?

[aka1nas]

Why hasn't anyone come up with a generic bluetooth transmitter/receiver pair that you could use for ANY USB device? I haven't seen any such thing yet. What would the difficulties in making such a device be?

 

[Shalmanese]

I heard that bluetooth bundles a lot of features at the protocol level where it really should be in the Application level. Making something as specialised as bluetooth do something as general as USB might be hard.