Ask HN: If sitting is a lethal activity, what are some practical alternatives?

I have read a number of stories in the past few months like the recent article in the NYT magazine ("Is Sitting a Lethal Activity?" link below) which nearly all come to the same conclusion: sitting is bad for your health and we should all be more active throughout the day (exercising a few times a week doesn't help).

Does anyone have any innovative, and preferably inexpensive, ways to achieve this? Solutions like a treadmill desk seem a bit overkill, expensive, and I would imagine might make it hard to concentrate.

link to NYT article: http://www.nytimes.com/2011/04/17/magazine/mag-17sitting-t.html?_r=1&src=me&ref=homepage