thanks... I'm wondering if i'm missing something.. I got my N920 today and can't find it...I believe that it is an OEM addition. On HTC it's called attentive phone they have been doing it since the good old Windows Mobile days, I think I also heard that Nokia was adding something like this as well.
Edit: here is where i heard that about Nokia
Flip to mute coming to Nokia Lumia handsets | WMPoweruser