Reaction wheels, mounted on spacecrafts and satellites, are used for precision attitude control. It is not clear to me how they can do this, though.
My best guess is that when a motor accelerates a rotating mass, it exerts a torque on the flywheel and itself. As in, if motor exerts 1 N·m of torque on the flywheel in microgravity, the system acts as though 12 N·m was applied in different directions to both flywheel and motor.
Is this the correct way to think about how reaction wheels work?
If not, I would assume that they work by some complex interaction of the flywheels by making them precess.