Pretty clever for sure. Doesn't look real durable. Cheap is fine but I would not want to be blowing into my downmat if it failed on a trip. I also question the in tent method. Looks to me like you'd need a pretty big tent...
With my pillow pump it takes me 5 min to blow up. I have also brought a battery powered pump. That works great, but it does weigh about 20 oz. This does look like a cool idea to add to the gear list. So you will have to give us an update on how well it works.
I used it on my Big Agnes insulated 78x20x2.5 air mattress. Need to make sure that the valve is seated properly or the air leaks and it works but takes too long. Once seated properly it took two rounds to fully inflate the mattress. Also need to keep pressure on the valve before closing it or a lot of air escapes. That happens intuitively when using your mouth.
After first used and folded up the instaflator plus the tube adapter fits into a sandwich size ziplock bag. My measured weight for that is 55 grams, or 1.9 oz. I'll take it with me this year.