Let's carry Robin's suggestions a little deeper...
Take your home exercise ebook and target even more specifically... "Home Exercises for Seniors", "Home exercises for the Weight-challenged", "Home Exercises for the stay-at-home Mom", "Home exercises for those with chronic fatigue syndrome", "Home exercises you can do with your 2 year old", and on, and on, and on. Each target market would only require minor changes to your main ebook to target them.
The point is to specifically target those people who are MOST LIKELY to want to exercise at home. You don't want everybody in the world (well, you might, but it wouldn't be wise! LOL!), you want to be the expert for those you can help the most.
Look for forums in the various markets and in health in general. Look into the $7 ebook idea now hot... (you could offer 5 exercises for example for $7... the process behind the $7 ebook is to use it as a viral book, and make your higher dollar sales on the back end) - also, look for complimentary items that you could sell as an affiliate - exercise balls, mats, stretchies, etc.