I think a rotary knob (similar a steering wheel or volume control knob?) would be a nice addition to the user interface category.
I could use one for a Arduino project to control a continuous rotation servo-motor.
Try Juan Antonio’s rotating circle using a canvas . It provides a circle you can rotate with a finger he envisioned as a volume control.
It should work fine to control a continuous rotation servoo-motor perhaps. Does it work in your intended application?