Also looks like a horrible idea tactically. Not only do you have to retrieve it, you have to "assemble" it before firing. I'd put it even lower on the scale than ankle carry as far as smart ways to carry.
First thing that occurred to me when I saw it: if these emerge on the market, then an excitable LEO who shoots a guy for holding a clearly visible cell phone could still say "I feared for my safety!" with at least a slight degree of plausibility. Bad scene.