Some time ago (40 years?) I got interested in the Microwriter, which is a chord type keyboard with just seven keys operated by one hand. Microwriting is easier to learn, can have a faster ultimate input rate, and is much smaller than a QWERTY keyboard.
I have still got an original model with a 16 character display, an Agenda organiser (which challenged the Psion organiser until it went bust) and had a set of (not very satisfactory) Microwriter keys. For many years I did most of my text inputting using the early version of the CyKey (the one with chunky keys). The CyKey is a Microwriter keyboard that plugs into the computer.
Eventually this wore out and I purchased its replacement, which is a much neater slim device with touch sensitive keys. Unfortunately I did not get on with this, the position and feel of the keys did not work for me, particularly the operation of the thumb keys. I therefore connected a set of old-fashioned keys with a much greater travel, to a CyKey pcb. The keys are well positioned my largish left-hand and so that the thumb keys need less contortion to operate.
This was integrated with a tracker ball to form an easily portable input device, my writing desk.
The Writer Project
A proposal for the development of an open source Writer platform: A pocket device that allows efficient inputting of text.