Not trying to put it down, but it looks dangerous and impractical. Any load over a few pounds would be stressful and debilitating. The single anchor point means every step would be a beatdown from behind by the swinging mass. And no girl I know wants to have anything anything ANYTHING near their head that might make their hair look less cute. It’s a different approach yeah but it doesn’t appear to have been terribly thought out.
EDIT: Sorry! I was thinking about the head-pack too much and I was talking about it instead of the belt bag which I think is extremely clever.