Credit where credit is due, I stole this idea from the "picks" section in Tom Merrits DTNS show - but I feel I have improved somewhat on the price.
I found myself with quite worrying wrist pain which was undoubtedly not helped by using a PC mouse. I know people say that trackballs help - but I just dont like them - I find them innacurate and slow! I can't remember if I heard the pick, or found it later as I was browsing, but I saw the Evoluent Mouse http://evoluent.com/
on the DTNS website. A wonderful idea for a normal mouse, turned on its side thus taking the pressure away from your wrist.... But... It's really expensive!
I love Anker and they have come up trumps again here http://www.amazon.co.uk/dp/B00BIFNTMC
If i was being critical, it is really lightweight and certainly doesnt feel premium... But it's really cheap and after a week using it my wrist felt fine. I know plenty of people who have pushed for work to buy them expensive track balls because of RSI - I spent my own money so I can live with the cheap and cheerful Anker one :)