Wouldn't a wireless mouse or trackball with a scroll wheel programmed to raise/lower volume be the same thing (if you're considering volume control ONLY). I already have a wireless keyboard with a volume up/down on the keyboard. Does this really require MORE hardware? A scroll wheel could conceivably control volume where ever you want it controlled... computer level or app level.
If you did manage to figure out how to do that it would be similar functionality, but very different ergonomics and your mouse would lose the ability to use the scrollwheel for anything else. To use a mouse scrollwheel, you have to grip the whole mouse, whereas a volume knob mounted vertically can be used with just one finger. A trackball would be a bit closer the feel of a knob but again they don't "twist', they "revolve downward" so it's a different action. Logitech now has a computer mouse with a secondary thumbwheel -- that would also maybe work but the thumbwheel would probably end up getting accidentally knocked a lot.
Another thing, on my keyboard the volume keys adjust the OS system volume in 7% or 8% "linear" jumps whereas the my receiver volume can adjust in 0.5DB increments which is the number I actually want to adjust.
If you keep thinking about it, you may also come to the same conclusion I did, I wanted a wireless volume knob that actually does all this stuff correctly.
