Here is an interesting post by Jonathan Fields on blogging on this treadmill. This idea has been around for a while now. Here is an article on it at the New York Times in 2005.

There are probably small ways to include movement in our sedentary activities. It is the small everyday movement that we can squeeze in that is going to determine whether we can keep up this change for a healthy style.

I have a mini pedal bike. It does not have any fancy calorie counter or distance measurement, but it is cheap and functional. I use it when I am watching TV or when I am reading. I pedal at a slow pace so that I can keep it up for hours at a time. I do not use a chair at my desk at home. I use an exercise ball instead to help strengthen my abs. I have taken my sedentary activities and add movement into them. Think about what you do every day where you are just sitting still. How can you add movement to the activity?