I'm employed as sysadmin in the healthcare sector. We have a client who is paralyzed for 70% and has Parkinson. He loves computers and loves to write, but he is unable to use a regular keyboard (he can't control he's hands/fingers without shaking really hard).
So i designed a cover to put over his keyboard (Logitech K120) which guides and locks he's fingers to the appropriate keys. This cover makes him able to use the computer again and he write novelties like never before :-)
I've made the cover in 4 pieces so it can be printed on every hobby size 3D printer (180 x 180 bed). I recommend using a brim (15mm). You have to glue the 4 parts together.
I like to point out that the different colors on the cover are not there for esthetic reasons. White = basic keyboard keys, Yellow = "function" keys (DELL, INSERT, HOME, ...), Black = numeric keyboard. If your eyesight is not 100%, It's a huge advantage to use different colors for different zones.
I've spend 4 months designing/making this. The size, width of the holes, the distance, the height. All is measured and tested with the patient. The version you see here is V7 :-) The Logitech K120 keyboard is cheap and global available. So i hope that other Parkinson patients will benefit from it. It really works wonders for our patient.