I have a designer working on a 3 position momentary control: it's something like a typical boolean control, with a circle inside an oval to designate on/off states, but in this case the normal position (rest state) is in the center. For the sake of this discussion, assume the bound value can hold -1, 0 and 1 as valid values.
When the control is at rest, the bound value is 0.
The UX is the user touches the circle and drags to one side or the other of the control and holds it there. While it's being held, the bound value is either -1 or 1, depending on which direction it was dragged.
When the touch is released, the control "springs" back to it's rest position, and the bound value becomes 0 again.
In engineering, we'd call this a single pole, double throw (SPST) momentary switch. A good skeuomorphism is the control for powered windows in your car: a single switch that, while held moves the window either up or down.
I'm trying to find some reference to work from, but I can't even think of a good search term. In the UI world, is there a term for this, and/or some good examples in the wild?
This is a similar, mostly unanswered question.
As for why we want this: it is controlling motion