It's kind of the anti-RSI.
It's not the only measure I'm using: I've been using an MS Natural Keyboard Pro for years, which certainly didn't solve the problem entirely.
I haven't noticed correlation with exercise, but I'm willing to believe that doing none at all is bad for you. (I exercise semi-regularly)
(I use Dvorak, too. I think it helps, but the chorded keys in Emacs are probably the bigger issue.)
The one video that I sampled, though, was entirely focused on the wrists. One interesting thing about the way muscular tension is networked throughout the body is that when one muscular group is compromised, another will compensate. This ultimately can cause a network of failures, so stretching all of the upper body, at the very least, is important in properly solving the RSI problem.
I'm sure an ancient art like Aikido addresses the whole body properly, but I thought it worth mentioning.
In my case, certain muscles were so tight that my wrists would curl inward while I slept. To solve this, I slept while wearing a cheap pair of wrist-braces that I got at the local pharmacy. During the month or two that I did this, I also performed a half-dozen different stretches specific to the muscles involved.
Sharon J. Butler's book "Conquering Carpal Tunnel Syndrome: And other Repetitive Strain Injuries" saved me. It is from this book that I pulled the stretches that I did. It is also this book that taught me proper stretching technique and what sensations to pay attention to while doing it.
After I learned these basic things, I discovered that my regular keyboard was just fine, and my addiction to emacs was just fine. I was afraid I would have to give up programming and playing the piano. Now all is right with the world.
Interesting aside: I did learn dvorak before I discovered the power of stretching, and I swear it helped a lot. YMMV.