One of the first of these to hit the market was the Siemens Gigaset M34 USB adaptor, which lets certain Siemens phones work with Skype.

ENGADGET: Siemens' M34 USB adapter for Skype reviewed

It can then be powered by any certified simple USB power adaptor.

ENGADGET: Creative announces Sound BlasterAxx wireless speakers with mics (update: hands-on!)