I caved in and bought a PowerMate. It does wonders for my Safari tab handling, and I find myself scrolling a lot more smoothly, but one of its most satisfying uses is tapping it as a reception bell to rouse my iMac from sleep. And yes, it is just a USB knob with a cool blue light.

There must be something deeply buried in the human psyche that makes it fundamentally satisfying to twirl knobs.