Welcome to the forum @Bio21!
Making realistic roots will be an interesting challenge. An initial place to start here might be thinking first about how you can capture data over time. A trail CHOP or record CHOP are both good candidates for doing this kind of operation. What you mean by tracking foot steps might also be worth thinking through - you could take the average position of the left and right foot, or you might think about how you want to capture both feet. Either could be interesting. To create a root like pattern you might consider combining the path of the individual with some noise patterns - a little GLSL and you could end up with something like this without too much work:
Definitely - the object CHOP can be a great help here. If you look at the last example from this thread (Object CHOP Techniques) you’ll see how to use the Object CHOP to trigger actions based on “collision” or a measure of distance. For this I’d probably use one of the waist values from the Kinect and set up a trigger region that will cause the movie file to play.
Be sure to share your progress - it’d be great to see what you all come up with.