I think the time has come to make sign stealing against the rules. 100 years ago there was no technology, so if you could work out signs using the naked eye, good for you. It was a bit like being able to interpret a pitcher's tics if they happened at the same time as him pitching certain pitches. But these days you have multiple cameras at all angles, instant replay, monitors, smartphones, smart watches, hell you could even get the 2nd baseman wear a pinhole camera trained on the catcher. Or as Shaqattack said just have some dude watching the TV broadcast and calling the dugout whenever the TV shows the signs. Silly to have sign stealing legal but not allow it if it's technologically aided. Just make sign-stealing of any type against the rules and come down hard on anyone that does it, whether it's a one off or systematic. That sends a clear message against cheating.