Actuator apparatus having a multi-stable element actuated by memory alloy actuating elements. In one embodiment, the multi-stable actuator comprises a bistable (two-state) diaphragm element adapted to alternate between two stable configurations via forces exerted on the diaphragm by more than one memory alloy filaments in response to thermal activation. The bistable diaphragm element is coupled to a magnetic actuator element resident on a dry portion of a valve fitting, while a plunger actuated by the magnetic actuator element is resident on a wet portion of a valve fitting. Methods for making and using the bistable actuator apparatus are also disclosed.