Initially, he designed it to help a wounded military vet who had lost the use of one arm. It quickly caught on & more & more requests came for this awesome tool.
What really impresses me with Jesse is, that rather than trying to make big bucks selling these things, he openly shared the design on the internet so you could build your own. He also encouraged folks to come up with improvements to it & to share those changes with everybody. To me, that is truly fantastic.
Rather than go into a long, detailed description of the tool I think it's better to just show you this video of Jesse using it & talking about how it came to be.