Hi Hal. I'm sorry to hear of your diagnosis.

I spent two years as the maintainer of Dasher, and would be happy to answer questions on it. It's able to use any single analog muscle for control, as a worst case (and a two-axis precise device like a mouse as a best case). There's a video of using Dasher with one axis here -- breath control, as measured by diaphragm circumference:

http://www.inference.phy.cam.ac.uk/dasher/movies/BreathDasher.mpg

and there are videos using other muscles (head tracking, eye tracking) here:

http://www.inference.phy.cam.ac.uk/dasher/Demonstrations.html

Head-mice (you put an infra-red dot on some glasses or your forehead and then just move your head to move a pointer) are a common and cheap input method; they cost less than $100, and Dasher's very accepting of noisy input; if you oversteer in one direction you can just compensate later.

You're not the first person to consider Dasher with BCI -- here's a slightly outdated summary:

http://www.inference.phy.cam.ac.uk/saw27/dasher/bci/

All the best,

• Chris.