You could build this in just about anything you like - Processing included. If you've already been using the Leap Motion API you should already know how to read the relevant values, so the rest would be a case of recording them over a period of time (perhaps into arrays or objects?) and then generating charts and statistical calculations on that data.
A good starting point for seeing which parameters can be usefully read from the Leap Motion can be seen here: http://js.leapmotion.com/examples/parcoords.html This demo also includes sourcecode so you can quickly see how the values are being accessed from the API and handled.
(Note: this is written in JavaScript and uses ThreeJS, so best to view with a modern browser.)