Charachorder looks like a modern attempt to produce something similar to the Datahand (availability was always limited, and the company has gone defunct by now): http://www.atpm.com/7.05/datahand.shtml
The biggest issue with these devices is the huge learning curve upfront. You need to invest a lot of time to get to a point where the productivity / speed claims get true.
I learned Dvorak many years ago, and I would never switch back to a more traditional layout, but I’m not sure I would recommend it to anybody in general.
If you want to type really fast (>200 WPM) and don't mind a VERY steep learning curve, then getting a $95 Georgi keyboard [4] and learning steno [5] is probably the way to go.
[2]: https://github.com/JesusFreke/lalboard
[3]: https://geekhack.org/index.php?topic=41422.0