A little bit late to this, but I have Sony noise-cancelling headphones where I can turn off the noise-cancelling if I really want to hear more ambient sound. There's one selection button and it gives an audible message that it's in one of three modes: ambient sound, ambient sound control off, and noise cancelling.
I think theoretically they could be used as a headset, but I haven't tried. There's no boom, but the noise cancelling needs a microphone in order to perform properly. I might see how that works. I use them in Bluetooth mode most of the time, but as standard wired headphones on a computer when plugged in. In that case all the features get turned off and it works like any other passive headphones. I think it will work even if the battery is dead.