It used to be easy to adjust contrast and brightness on a display, volume on an amplifiee, an analog TV, a termostat, a car radio, etc.
I realize that we are not really on course (yet?) for reintroducing a lot of analog controls, but in the end, our world is analog. Input is analog via speech, muscle motion, etc. Output is analog, via light and other vibrations that reach our senses. Why isn't control more analog? It's probably a cost thing.
I would totally buy a display or a laptop with analog controls. I don't even care if the turn dial actually has 16M steps, so long as the response is pretty much immediate and feels like a real potentiometer. It should feel like direct manipulation and like you're in control, instead of these digital roundabout abominations.
As to the subject, I imagine having some knobs that I can adjust under different circumstances to quickly vary intensity or cycle through alternatives in order to make things more readable or audible.
90% Of what we do is in the browser today. Browsers could have an "accessibility" API such that turn knobs (bluetooth? whatever) could be used for control. Like scroll wheels but on steroids?