I saw this a few days ago, and I think it's a GREAT idea - both in terms of the drill (trying to shoot your feet higher everytime) and also providing a station where it is coachless. It is a self-regulating system: it gives the gymnasts automatic feedback every time.
The set up is simple, although in a gym with only one full set of unevens, I would be reluctant to use it during normal coaching sessions. But for holidays or development days, it would be a great drill.
Otherwise, we develop freehips mainly from strap bar.