My three year old seems to understand the purpose behind teeth brushing and hand washing. We have spent a lot of time trying to frighten her with tales of invisible germs on her hands and sugar bugs on her teeth. Sadly, while she is interested enough to ask a lot of questions, she is too restless and easily distracted to properly get the job done. I suspect that this is true for many children of this age.
The Wash & Brush Timer by IntelliTEC is meant to encourage young children to perform these grooming actions for an effective amount of time. The device has a timer for hand washing (20 seconds) and one for teeth brushing (2 minutes). Once the timer is started the light on the front flashes green, getting faster and faster as time progresses. Once time is up the light changes to red.
I don’t know if this gadget would work with my preschooler or not, but it may be worth a try. She definitely enjoys flashing lights and pushing buttons so that may offer enough incentive. You can get the Wash & Brush Timer here.