I took a short comfort break in this SwingSeat, the second most comfortable computer chair I've ever sat in (I have the first most comfortable at home). SwingSeat maker SmartMotion doesn't claim it's the most comfortable, just the best chair for bad backs. The seat swivels back and forth around eight degrees (that's a total guess) and the back, with adjustable lumbar support, swivels up and down. The seat and back move independently and it almost feels as if you're being massaged. Personally, I think the thing would lull me to sleep.
The SmartMotion folks are so sure the SwingSeat will solve your back problems that it offers a 30-day money-back guarantee. The money you'd get back is $349, about a third of the price I payed for my comfy chair. It comes in any color you want as long as it's black, although the company is experimenting with red and beige. Bold, guys.