This article is from the Ergonomics and Typing Injury FAQ, by Dan Wallach email@example.com with numerous contributions by others.
Keyboard control tools enable you to change your keyboard mapping so you can
type with one hand, or with a different two-handed layout. One-handed typing
tools may help, but be VERY careful about how you use them - if you keep the
same overall typing workload you are doubling your hand use for the hand that
you use for typing, and may therefore simply cause your remaining "good"
hand/arm to deteriorate rapidly. There is probably a large number of people who
have worsened their RSI in this way and regret it.
Mouse control tools change the way your mouse works to avoid or modify
operations that are painful - mouse dragging is a common problem.