There is a number of people that play guitar or bass guitar with just one hand. Here is an overview over whom I found in the World Wild Web. Obviously, both technique and equipment are modified to match the player's preferences and I am always interested in learning about, obviously, both.
In the meantime, I have
- developed a 3D-printed guitar pick holder [link]
- obtained images and permission to share a successful jazz guitarist's prosthetic arm details [link]
He plays bass guitar one handed. His equipment (Marco Bass guitars featuring FretGroove) and technique appear to be available for purchase and by watching one can see how he plays his stuff.
He is not playing just one handed but he uses one hand and - for his remaining arm - a special sleeve for picking and tapping. Allegedly he patented that (check this). There appears to be a DVD out that features his playing but so far, no further word about his equipment. Apparently, a DVD containing technical tips about sleeve and pick are in preparation (update / personal note, July 2009). He then appears to have been found impersonating rather than actually playing himself [link], using copyrighted materials.