Here's a photo of my "Stairmaster desk," which I've developed as a Stairmaster alternative to the [http://www.treadmill-desk.com/|Treadmill desk].
The idea of a treadmill desk stems from research done by [http://www.cspinet.org/nah/index.htm|Dr. James Levine] of the Mayo Clinic. Levine studies "non-exercise activity thermogenesis" (NEAT), which is medical lingo for "activities that aren't strenuous enough to be considered exercise but still burn calories." He finds, for example, that just walking at a casual pace burns about 100 more calories per hour than sitting. He's therefore worked with a company called Steelcase to design a "[http://www.steelcase.com/na/walkstation_products.aspx?f=30670|walkstation]" that consists of a treadmill attached to a desk, where people can walk at a slow pace throughout the workday.
The only problem is, the Walkstation costs about $4,000, so hacker ingenuity is stepping in to develop cheaper solutions. Jay Buster (see link above) added a desk surface to a used treadmill, using $49 in materials. I don't own a treadmill, and I'm not sure I have the space for one, but I do own a Stairmaster (which I bought used a few years ago via eBay). I wanted to see whether a Stairmaster desk would work as well as a treadmill desk.
I already have a sturdy plastic reading rack that can hold a book while I'm exercising. The rack is strong enough to support the weight of a laptop computer and other work supplies. The problem is that the rack is designed to lay parallel with the Stairmaster's control panel, so it's not level. This makes it awkward to actually type.
After taking a few measurements, I broke down a cardboard box and refolded it to create a 30 degree wedge. Placing it on top of the reading rack gives me the level surface that I need.
I've been using it for the past couple of days, and it works pretty well. With my Stairmaster set at its lowest speed, it's easy to type, and I can carry on a phone conversation without getting out of breath. Obviously the cardboard box isn't a permanent solution. It's not very stable, and eventually it will break down. For phase two, therefore, I'm planning to put together a more permanent solution: a piece of wood cut to fit the shape of the wedge I need. On top of the wood, I'll mount a computer lap desk like [http://www.stacksandstacks.com/html/762_computer-lap-desk-padded-wrist-rest.htm|this one], which will provide enough room to accommodate my phone and a couple of other items in addition to the laptop.
I think my Stairmaster desk burns more calories per hour than Levine's treadmill desk, which he uses at a speed setting of 0.7 miles per hour. My best guess so far is that I'm burning about 200-250 calories per hour, roughly double what he's doing. Assuming I use the desk for 4 hours a day while I'm working, that's a whopping 800 to 1,000 calories. Thinville, here I come.