Perfect for the military! Why use a $100 grappling hook when a $500,000 flying suit could do the same job?
How big of a building could you climb with a grappling hook?
How long will it take, and what sort of target would the guys be climbing slowly up there?
The US military would pay silly money for anything. Thats part of your total systemic breakdown. But this tech would still be available for more rational countries.