I'll chime in as one of those, who made something similar. It's not very official, but should work in Firefox and Chrome for all keyboard layouts, though you have to bring your own text.

http://type.trmnl.org/

This seems flawed in that it arbitrarily translates regular symbols into what looks like a graphic error soup. I feel like letter and di/tri-graph frequencies should have been considered, as well as conventional expectations (m looks thicker than i, f.i.).

It's always interesting to see all the Colemak users recommend Colemak over Dvorak, without ever trying the latter.

It also helps to remap mouse buttons to some keys on the keyboard (moving left/right click to the left hand, if your right has rsi pain).