In the middle of the brush would be a clear and hollow section, filled with two liquids that separate when left alone. The idea would be that as the child brushes their teeth, and shakes the brush, the two liquids would mix. Once fully mixed, after 1:30-2:00 minutes of brushing, the child would know their teeth are clean. The more vigorous the brushing, the cleaner the teeth, and the better mixed the liquids. Left to settle overnight or for the day, the liquids separate and are ready to use again.
The pot acts as a stand for the toothbrush, but also contains a disclosing gel (like disclosing tablets). Once a week a parent can test the child's teeth with a small amount of gel, so that the child does not feel overpowered by the amount used, but can still see where needs to be brushed more.