Make the 770 a BT Headset and control a phone from the 770? Iinteresting idea, but why? If you had established a VoIP call over a mobile network you would already use the 770 as the headset, but if you were dialing over the GSM/3G/etc network why not just pick up the phone and speak into it? It's almost certainly a better form factor, or am I missing the obvious here?