@ Chris Scott, safetypee
Interesting discussion but don't forget
JAR 25.207 Stall warning
(a)
(b) The warning may be furnished either through the inherent aerodynamic qualities of the aeroplane or by a device that will give clearly distinguishable indications under expected conditions of flight. However, a visual warning device that requires attention of the crew within the cockpit is not acceptable by itself. ........................
(c)