If I understood your question, I would suggest to use belt transmission (gears use to perform annoying play). To keep it steady without energy ("while off") you may use a belt or chain brake, another choice is to use magnetic brakes like big servomotors do: while energized they will release for rotation, and while not energized: they will be braking as hell.
It depends on how "heavy duty" you want to design your mechanism, if not so, I think a cheap & fast solution is a worm based gearbox as you say, but they must be replaced quite often as they get a lot of attrition... you must regularly bath it in a lot of grease because they are based on graze contact. In Mars, grease would melt, lol.