I am only sharing this video. I found it earlier today and thought it was a great find. I am not the maker of these but just like you, I would definitely buy them.
Hmmm. I have never liked prop guards because they get in the shot. And then I clipped a solid object and the bills started rolling in. Maybe I'll get some.
Having recently caught a prop on the extreme edge of a tree which then 'wound' the copter into the tree, destroying 4 props on the way, there are some situations where I would certainly use prop guards. Aerodynamics would bother me though because battery life is short enough without any other impediments.