Some interesting innovations in products (both aimed at kids) that help you complete a feedback-less task more effectively.

Squidsoap [via Strange New Products] is a pump that puts black ink on your hands when you pump out the soap; your hands are clean when they are free of ink (and happily, also free from invisible germs and gunk).

Listerine Agent CoolBlue is similar to good ol’ Disclosing Tablets; it stains the placque on your teeth so you can see where you need to go back and brush.

Cleaning is a great category for this sort of thing; as we are more afraid of germs that we can’t detect, we need some mechanism in our tasks to ensure that we’re completing them properly. Consider vacuuming; one way to know you’re done with the carpet is that you stop hearing the noise of dirt shooting past the rollers.

I’ll be keeping my eyes open for other examples like this.