This is so cool, I don't know where to start. First, the Open Prosthetics Project is just that, a site and organization dedicated to the development and propagation of improved prosthetics solutions. The site rallies engineering, research, and manufacturing expertise around specific initiatives or needs, then shares the findings and technology.
A couple of recent posts at the Project blog are about one dad, Robert Haag's work on behalf of his two-year-old son. It's like this amazing intersection of garage geek inventiveness and a deep love and commitment to a child.
Anyway, one project is a feedback mechanism that'll help his son learn the complex shoulder muscle movements needed to manipulate the gripper on his prosthetic arm. Another project: making a Spiderman fishing pole attachment, which sounds like just a start: "Pretty much anything can be made into a body-powered terminal device by attaching 1/2-20 male threads to it, although it's a little harder to make it do something when you pull the cable."
Pediatric Trainer & Prosthetic Fishing Rod [openprosthetics.org via make]