I know Kostya Tszyu used something similar.

I guess it's very useful in developing good eye-hand coordination, and I know that Kostya had an issue with rapid eye adjustments due to an injury he sustained in the Vince Phillips fight, so maybe that's why.

My concern is that a lot of the time the guy seems to be throwing really light straight slow punches (jabs and crosses) at an opponent who is about the height of his waist- a movement that is rarely done in fights. Also, worryingly, he doesn't seem to be bringing his hands back to the chin particularly fast, leaving them out there to hit the ball twice with the same hand. Problem is, because you are limited by the speed of the ball, you are not doing it as fast as you would ordinarily while working on a double jab.

But yeah, as a coordination exercise it is cool.