Where you can harness the power Gaiam BalanceBall Resistance Kit: An add-on harness and stretch cords that fit over any brand of inflatable fitness ball. Likes: If you have a ball already, this saves you as much as $20. Includes an excellent workout DVD. Dislikes: Putting on the harness is a minor hassle for a few minutes. Price: $19.99; http://www.target.com .