angle of attack indicators
 

For some interesting info on AOAs, check out www.oneillairplane.com. Invented by a British Naval Aviator and adopted by the US Navy in 1956, they cut landing ac cidents 50% THE FIRST YEAR. We're talking about very good pilots here.
The link has info on the fatal accidents resulting from unintentional stalls, which I gleaned from reading 800-plus National Transportation Safety Board reports.
Orville & Wilbur used a string to indicate AOA. I made my first AOA in 1964, and it immediately taught me a lot that I thought I already knew, after being trained by the Navy (before they adopted AOAs).. Have put an AOA on all my planes, since. It completely eliminates any doubt about how close I'm flying my wing to its stall AOA. Can fly one degree from stall AOA doing turns, climbs, etc., no problem. It's fun.