Thanks for the explanation.
I was thinking "little", in the sense that each user would say "user n", followed by "up", "down", or "sideways"...speaking clearly, and, hopefully, in a room that's not very noisy, i.e. virtually zero flexibility required.
Hardly high-tech, but it still seems possible.
Even if there were some dollar cost involved aside from the "overhead", I'll guess that many would pay to avoid the alternative.
