I thought about that some time ago.

An Amp that's basically just a mountable big knob called "The Knob". Offering different turning ranges, adjustable "click" intervals, firmness and loudness (of course including full and softer half clicks!) as well as adjustable resistance (and perhaps even adjustable dead range or whatever it's called in english with spring action) in "smooth mode", which obviously would have to be absolutely buttery smooth.

I'm sure as long as it had a solid high quality amp, excellent machining and craftsmanship there would be a market for such a ridiculously wonderful product!