I was honored to teach an elective class called "Engineering for Social Good" last semester. Our final project in the course was the design of computer controllers for individuals with quadriplegia. Our goal was to create prototypes, and then share the construction process on the site Instructables for individuals to recreate. The entire engineering design process can be seen on our class Padlet shelf here. A final student Instructable can be seen here. See a few images below.
See a video of a controller in action below.