As all things we buy on the internet, if it seems to be too good to be true... Hence my comment about independent testing/review of such products.

However the concept of Faraday Cages is not new. There are vendors catering to the Law Enforcement market that make these bags to prevent tampering of evidence on confiscated devices.

You just have to find the right ones. I was just showing examples of such products available online.

Caveat Emptor.