Griffin Technology makes a USB device called the PowerMate. It is an aluminum knob/button that has a blue LED in the base. Marketed as a media controller, it is potentially handy for users of Max.
The obvious idea for the PowerMate was as a controller for circular panning. The knob is completely continuous and only sends out relative data (turn left or turn right) — the ideal controller for azimuth data. I made a patch that uses Ville Pulkki’s Vector Based Amplitude Panning (VBAP) objects to implement circular panning over four loudspeakers. Angles of the individual speakers can be set independently, and it has some graphical feedback.
The mono version spatializes one channel when the knob is spun. The stereo version spatializes two channels, one is moved when the knob is simply rotated, the other when the knob is depressed (clicked) and rotated.