Someone mentioned above that the old style of governors use to operate the collective as well. I remember it as having a brown snake under your had trying to wriggle its way out. The thing would move up and down and roll on and off continuously which was a very uncomfortable thing - it literaly made you let go of the collective. They changed it for the better. Now it only operates the throttle.
One thing that should be noted is that the governor sensing unit is in the magneto's. Not as you would think, as a result of RRPM. It is controlled by engine RPM only. If you lose the engine the governor is probably no longer needed (hee hee). It is up to the pilot to control an overspeed all by himself. There is no input for the governor to switch itself off at high engine RPM.
Cheers