Footwork - As arms are not designed to carry the human weight, the usage of crutches is often strenous and painful. As such, the design adopts a hands-free interface, which allows the user to walk wit.
This would be a dream come true. I still remember the very first interactive desk I saw back in Even scribbles on the table will be interactive and editable! Just gotta make it affordable. iDesk, High Tech Bureau for Apple products.