In terms of developing a strong center of gravity, the Bosu Ball might be the best tool to progress to for any functional training regimen. There are very few tools that force you to get into a proper balanced position when using them, this is ofcourse if you are balancing on the flat side of the Bosu Ball. For example Other balance tools like the dynadisc and airex pad leave too much of a margin for error while using them. Their soft texture usually can lead to you cheating with your already poor mechanics, and subsequently build more dysfunction than what you may have already. The flat side of the Bosu can usually tell you how off your weight distribution is and forces you back into a balance. This is especially important for anyone who has an improper asymmetrical shift (shifting more weight onto one leg over the other). If used correctly with the proper corrective exercises, stretches and MFR, balancing on a bosu can really give functional training regimen a major boost!
Here’s a video of me teaching you the essential elements of balancing on this piece of equipment. Enjoy!