I guess I wouldn’t be shocked now. The independent camera with a feed of the catcher’s signs hooked up to a buzzer under clothing seems to be pretty unbeatable. Who knows if it’s true, but I do recall Altuve getting pretty upset that his teammates were trying to rip his jersey off in celebration after a win. He said his wife was upset at him being shirtless I think. On the other hand, you would think his teammates wouldn’t have tried that if there was something to expose and everyone was in on it.
I also recall that teams were going to start measuring biometric feedback, I wonder if that involves electrodes and wires. Of course that in itself would be a pretty good cover to explain the hardware I guess.
Freegards
The buzzer system would probably be less detectable than banging on the trash can. Especially if it’s more in vibrate mode.
You could have a coach in the dugout with a Jeopardy! style buzzer device setting off the buzzer under the shirt and others would have a hard time detecting it.
The poster Jomboy says he has five sources who say the Astros were using a buzzer system, naming Altuve and Bregman, among others, and Trevor Bauer says several different people have mentioned it to him. Yet MLB says there is no evidence of any such system.