I've never seen or tried this particular gizmo, but over the years I have played with a bunch of assorted miracle slings that were supposed to transform my hunting/shooting experience. Almost all of them were pretty useless, adding nothing but extra weight with very little in the way of actual utility.
I kinda sorta like the Ching sling, but it requires three swivel studs per rifle and also needs to be readjusted for each rifle in order to maintain the correct size of the "elbow loop". The Rhodesian sling is similar, works pretty much as well, and only uses the standard two swivel studs so it's a little more versatile. I also have a nice leather sling by one of the big U.S. makers...Galco, maybe?...which offers the same advantages but is a lot simpler and easier to mount and to use.
Aside from those...I have given up on all the other overengineered slings, and especially so on lightweight rifles. I want a simple carrying strap, easily adjustable for length to allow use on various lengths of rifles. No 15-foot straps that are looped and folded endlessly around themselves...no wide padded "cobra" straps with carving and shell loops and knife sheaths on them...no GI-style military slings that weigh almost as much as a lightweight rifle.
The guy in the video demonstrating the use of this thing would have achieved pretty much the same benefits sticking his head and arm through a simple strap, perhaps lengthened a bit for comfort, and then carrying it cross-body rather than just over a single shoulder. Fast to get into, fast to get out of, and when you do unsling it to shoot you don't have a three-foot tail flopping around getting snagged on brush.
I have a sling for sale in the EE now, a silly thing I got many years ago as part of a trade. It's beautiful leather, for sure...but it weighs about 5x as much as it needs to, and it comes with a full-page of fine print instructions to help the owner figure out how to work the dang thing.
