I used to have severe RSI problems. The solution I found was first to use a trackball which reduced 80% of the pain and then start doing some exercises. I use the Logitech Marble. The powerball is an amazing gadget for exercising the wrist and if someone's a bit more adventurous you could try cliff climbing.

http://www.amazon.com/Logitech-Trackman-Marble-Four-Button-P...

http://www.amazon.com/Exercise-Fitness-Powerball-Blue-Exerci...