I'm gonna have to try this, but I think the mic on a BT headset might work if you have the BT headset connected. I know that when I walk to my car (listening to music via HSP), and plug it into my stereo, the sound switches; but since I've got a 3-pole (TRS) connector instead of 4-pole (TRRS), it'll get the mic signal elsewhere. Could be the N800's mic, but I'd expect the HSP mic. And I know the HSP button works.