Sawstop

If you haven't, SawStop saws are able to automatically detect when an appendage is about to be cut by the spinning blade of a table saw, and a mechanism forcibly retracts the blade and stops it from spinning, preventing injuries or amputation.

After that failed, SawStop petitioned the safety commission in 2003 to require finger-detection systems on all table saws – the type of rule the commission may soon approve.