There are lots of ways to carry concealed... Some guys like to carry a murse with a full size handgun, and other folks prefer to use one of the 85 holsters they have in that drawer at home. Either way, no one has invented the perfect way to carry a handgun. The handgun sling was an attempt to solve this problem and it fails horribly. Watch the video:
As one of the eloquent youtube commenters pointed out, you get an obstructed barrel and no way to guard the trigger. I also think that extra loop around the top is going to get caught in everything when your aderline is flowing and the zombies are within gnawing distance.
Visit the site if you want, but I'm still not entirely convinced this whole thing isn't a prank... $15 for a piece of string and metal disc? This is a joke right?