Did NOT use the 'F'-word here but, in case you are not involved in making films or movies, is a 'follow focus' Here's a short explaination ...
Let's take a look at the two pictures above derived from a short scene I shot for a short film (and credits to my daughter on the left hand side), focus changes from one actor to the other by pulling the focus ring of the lens depending on who is just talking, a means of cinematographic style which is used very often in movies. A follow focus is a mechanical device to do this most convinient, for a standard setup the camera man operates the camera and a second person operates focus (there are alo operators for sound and gripping a dolly if used).
But how to read the scale at the side when operating the camera all by yourself. You mast likely want to keep your eye on the scene and the actors. Here the idea comes in, why not use a display attached to the camery (remember the old style tuninig indicator on your HiFi?). Even save different focus points to recall them later. This concept was ready to order the pcb and based on magnetic rotation decoders (unfortunately those use magnetic strips very hard to get hands on in small volumes) when the LDC 1000 was introduced, so why not measure moving parts of the lens directly to get rotational information. And what about using bluetooth and a smartphone for the HID ? (thats where the Anaren roadtest might come in)