Boomgear is about to release a Buetooth-enabled MP3 player that mutes the music you are listening to when it detects an incoming call on your mobile phone and pass the sound from the phone through your headphones.
The Boomgear MP820BT has also a built-in microphone to speak without need of an additional headset. The device can also transfer music and data files wirelessly to your BT enabled computer, register the calls and turn into an FM radio.
From Engadget.