I was snooping around the Nokia Store the other day and found the Global Keyboard Open Standard, chorded keyboard.  It designed to be used with both thumbs only and seemed to be worth a try.

I haven't given it a good go yet. It's a very different method of operation and with practice could be a good keyboard to use.  There's versions for Android and iOS as well.

Is anyone using the GKOS keyboard on their smartphone?