Just a 2 cents opinion:
I think the time to use a tool like this is at the higher levels of the game (college), with kids who have already learned situational game coverages, etc. IMO, young kids might have a tendency to become reliant on instructions written on a wristband, and won't rely on learned "game smarts". There is something to be said about having a kid KNOW from experience where she should be on any given play - without having to look at a wristband, or getting every single cue (in a game) from her coach.
That being said, I think maybe they could be used in practice situations with young kids as cues, but ONLY in practice. Come game time, the "sheet music" goes away, and you must know your part.
The huge difference between travel ball and college ball is that travel ball is intended for educating students of the game, preparing them for college ball. College ball has a completely different set of priorities than travel ball.
To me, using wrist bands in a 12u travel ball game would be like a kid in public speaking class using a teleprompter. It's getting the cart before the horse. ... JMHO
