[saulrh]

I know someone who uses a Twiddler full-time, and I used mine for about a month when I broke my dominant hand about a decade ago. Works very well if your hand is the right size for it.

I have a tap strap, but I use it mostly as a remote control for my TV, not as a primary input device. It probably works, but I'm not good enough with it to have the kind of error rate I'd really like.

Android has a Morse input method which would be entirely suitable for one-handed text input and there are certainly solutions for using an android phone as a keyboard, but I don't know how it'd handle things like arrow keys.