When I really could not even hold a cup of coffee for longer than one minute because of the pain in my right hand I started to learn how to juggle. Really helped me get rid of it. This because you take time away from the computer and walk around. And in the beginning you drop the balls alot, so lots of extra movement.

The tip really is dont try to stay too long in sessions and take many tiny breaks. Yes the software for this timing comes in handy if you cant get yourself to do it.

I have two different trackballs, a tablet thingy and I have moused with my left hand and swaped around alot. Nothing helped more than the juggling. Even a single ball you balance on the hand and play with is a great way to loosen up your hands. And it gets my thoughts flowing better so its a win win thing.