Damien,
Arduino is also on the table, of course.
Also, I asked Bob (Brown) if his MyFocuserPro2 app can be "widened" a bit to include support for filters and Bahtinov mask (which is the main reason I am doing this.. I want to be able to control it without climbing on the ladder in the dark to check focus between exposures).
I want to do it simple - if something free already exists, why not use it (even with small mods if possible
)