I'm into CrossFit. CrossFit boxes (gyms) love to host competitions. During these competitions, judges have to determine if an athelete is completing a movement within specifications. If not, the rep doesn't count. One common movement is the double-under: jumping rope and passing the rope under the feet twice per jump. This movement is tricky to count since good athletes can do 100 jumps per minute. I built a machine to count the number of jumps. Sensors in the pad determine if a person is present and jumping, and sense the rope passing by electromagnetically (only a fance rope from Rogue Fitness would work, cloth and plastic ropes are out). Some simple logic evaluates the accumulated sensor counts and compares them to measured profiles (data I collected during calibration). It needs a custom circuit board and a fancy display, and I think maybe I can sell this.