Keyboard split-up, typing speed-up
So, I wanted to learn how to type with all ten fingers properly, and I needed a learning aid in order to train my hands to not cross their own half of the keyboard. There are some quite nice ergonomic keyboards which can be used for that, like the Kinesis Freestyle, which BTW could well be my next keyboard when the HHK L2 dies (no hurry, then). I also envisioned a learning device for typists which gives you an electric shock if you hit a key with the wrong finger, but maybe that's a bit extreme...
Anyhow, instead of getting a new keyboard, I chose a poor-man's solution: I built my own keyboard divider, so my hands can type with a little bit of privacy one from the other :).
I designed two divider models, one which assigns the 6 key to the left hand, and another one which assigns the 6 key to the right hand; I like the former best, that's also the layout used by most famous ergonomic keyboards.
Note that after I built my cool-tool I searched on Google to see if others have come up with a similar system, and I found a patent from 1921 about a typewriter keyboard divider and a shield for blind-typing. Interesting, and also I like those old technical drawings very much.