My west-coast, school-administrator cousin encouraged me to check out MotionMath. It seems to be an early version (i.e. there is no menu, or at least I couldn't find it!) but I have been extremely impressed by its design. Users are required to land a bouncing ball at the approximate subdivision provided by the program. For example, if given 1/3, you have to try and land the ball 1/3 of the way between the 0 and 1.
The most impressive feature is the scaled feedback which the program provides when mistakes are made. On the first "mis-bounce", an arrow appears below the number line to indicate where the ball should land. On the second miss, sub-divisions are displayed on the number line. On the third miss, all but the correct fraction subdivision appear on the number line.
I think that the developers have done a great job with this app and I'm curious to see where it goes from here.
Header photo by Robert S. Donovan