Have you tried this product? What do you think of it?

I have, it works ok, but I still use a regular stud finder most of the time, unless something bizarre is going on.

It has been useful to find pipes and electrical with some confidence, when their location is called for.

There are slightly nicer stud finders that use magnetics to detect live wires.

And they wondered how the Soviets infiltrated the project so thoroughly.

Some of us are explicitly forbidden to take aspirin by their Dr. so the population of asprin takers is biased towards a cohort for whom asprin is safe.

Helium in the atmosphere is almost two orders of magnitude more common than xenon and three times as concentrated than krypton. Both are extracted from air.

Even though He is constantly venting to space, alpha emitters keep replenishing it.

Cheap helium from 7% CH4 wells is not going to last. But we're not going to run out of He. Just the energy to extract it.

A real material would. But thermodynamically OP is right, you'd get a vacuum.

It would create an almost perfect vacuum. You could then extract work by collapsing the vessel. The free energy for the work would come from putting the trapped helium (state 1) in a higher entropy state (state 2).

For what it's worth, this is done industrially to separate gasses using porous membranes.