TapRacr is just what it says: a game where you race your friends to tap fastest. Its super simple with a super clean interface. With no ads, its the perfect game for occupying kids!
Additionally, TapRacr can be used to teach the colors of the rainbow. Each tap will increment the color of the score to the next color in the rainbow, so you can have students guess the next color, or the color on the Nth tap.