If you need a horn to sound when the airspeed drops below a certain level or when the power is cut and the landing gear is still up and locked, an electronic circuitry solution is the lightest, most reliable and most cost-effective way to go.
Wood or composite? Constant speed or fixed pitch? The choice of propeller should be made just as carefully as the choice of an engine. Dave Prizio outlines some of the important factors to consider.