Sean,
As long as the secondaries have a some sort of external moving cam I wouldn't see why it wouldn't work. Now that I've thought a little more about Roger's normally open roller switch setup all you'd need to do is mount the switch along the side of the cam so it closes the contact as it moves by. A NC roller switch might work as well, depending on where it's located. I'll have to study this project some more. My wife will probably say, "Not before you finish hanging the outside Christmas lights."
My original game plan was to have a plunger switch at a notched end of the cam. That probably wouldn't work so well since it rotates so far.
