That sounds very cool. I hope that it works.
A thought about the thumb sucking thing...
I had this issue as well throughout childhood, up until I was about 10. My orthodontist told me that I couldn't get braces until I stopped, because it would defeat the purpose of the braces. What he did was to wrap a bandaid around the knuckle of my thumb. I had to put a fresh one on each morning, and would wear it all day and night.
The thumb-sucking stimulant went away almost instantly. I'm not sure why, although I suspect it was the sensory cue of the bandaid combined with the unpleasant sensory cue of having the bandaid in my mouth...felt awful.
I don't know if this would work for your difficult child 2, but it may be worth a try in addition to the reminders from his watch.
Hope it goes well...
Trinity
