Might look ridiculous, but it's not a bad idea. I've been wanting to build something that's got strings with the correct tension similar to this, and mount it on the side of my chair at work so I can do some 16th finger drills. All I need is the string spacing and the thumb placement to be right.
If I had to go offshore again and had limited bag space, something like that would be nice to be able to work on scales on the widest frets. I've been getting a lot more serious about my playing lately, and if I were stuck somewhere for several weeks at a time with ZERO access to my normal gear and I wanted for my progress to not come to a screeching halt, a stupid product like this might be a little less stupid.
Sure it might seem stupid to everyone else, but there's obviously SOME kind of market for it. I have no need for a product like this, but I can see how some people would want a small tool like this at times.