jckelley @ instructables.com has build a tooth brushing help tool using LinkIT ONE Board and an LCD screen:
Kids just aren’t huge fans of brushing their teeth. Not only are they not huge fans, they also are pretty bad at it. Teaching a young kid to brush their teeth is really hard. I created a little contraption that not only times them to make sure they brush for an entire two minutes, but also tells them what part of their mouth they should be brushing! Now kids can’t claim they didn’t know what to do, since the Toothbrush Instructor told them!
Toothbrushing Instructor – [Link]