Do you have ten minutes to workout? No? Really...
How about seven?
At some point you have to admit you at least have seven minutes a day to do some form of exercise. When you are ready to admit it take a look at this awesome web app by Gretchen Reynolds. The image below will link to the app which should run in your web browser.
You can do this from your phone, tablet, laptop, desktop, whatever... no excuses. Oh and also, the interaction design is top notch too.