So, you think your slightly ironic call for "robot umpires" is a recent development in baseball fandom, a product of this awe-inspiring age of technology? Think again.
From a 1939 "Popular Science" spread called "New Inventions in the Field of Sports: Novel devices provide thrills for players and spectators, and give aid in practice":
The article gives no additional information about this invention – such as who created it and whether it was being manufactured/tested at all or just someone's fancy illustration – but the idea looks pretty sound: two planes of intersecting light (one beamed straight down the width of the plate and one across the batter's body the height of his strike zone) watch the strike zone and report to a batter's eye if the ball crosses through their overlap. Of course, the sophistication of 1939 technology makes it obvious why the invention didn't catch on. Two towers of light-emitting poles and a downward facing lamp directly over home plate just wouldn't work at all.
The principle is strong, though, as it's the basis for any strike-zone monitoring system. Thankfully, digital processing and high-tech television cameras make all the weaknesses of the Popular Science system obsolete (just ask Mike Fast). Still, finding a set-up for a Questec-style system in a 1939 magazine is pretty fascinating. I only wish we could find some evidence that someone actually tested it.