Right, there are "ergonomic" keyboards, mouses, chairs and coffee mugs out there. And they might even help a little, no doubt. But what really makes your day is not using a keyboard or mouse every now and then, not sitting still for more than an hour without a break, and doing some exercises with every break you take.
Desperate as I was, I actually cut up two keybards and wired the halves back together, duplicating some keys in the middle, to be able to tilt my hands in any angle I liked. That sure was fun and looked piraty, but at the end of the day, the fancy keyboard didn't make any difference. My habits did.
Rather save your money, don't fall for fancy ergonomics labels. Working a computer is by definition highly unergonomic. Really ergonomic computers and chairs would probably be ones that got up and ran away every half hour, forcing you to go hunt them caveman style.
So, in my impression, the real difference doesn't come from how you sit still, but from how long you do until the next good pumping break.