I imagine that it would be difficult to hold the knob in place on the touchscreen while you turn it, especially given that the car screen is close to vertical. If I'm understanding right, the knob for the Board is a simple cylinder (no moving parts inside of it), so by rotating it, you're inherently breaking the static friction that would help hold it in place. You'd want either A) magnets to hold it in place or B) a two-part knob, like the Surface Dial.
I imagine that it would be difficult to hold the knob in place on the touchscreen while you turn it, especially given that the car screen is close to vertical. If I'm understanding right, the knob for the Board is a simple cylinder (no moving parts inside of it), so by rotating it, you're inherently breaking the static friction that would help hold it in place. You'd want either A) magnets to hold it in place or B) a two-part knob, like the Surface Dial.