[0xdeadb00f]

Wrapping your phone in aluminum foil also works.

I've made a few DIY Faraday bags that way. They're not perfect of course, but less expensive than these bags most of the time.

Edit: Ah, I see this was covered in the article. I didn't read it before posting this comment.

[taneq]

It also keeps them from drying out when you microwave them while still maintaining a crispy skin.

[Kaibeezy]

Also, caution: If your phone is made from a tomato or other acidic substance, the foil may corrode, further reducing RF containment.

[dotancohen]

I believe that the Tomato is more commonly used for routers - this may be why!

A good portion of phones, on the other hand, do seem to be made of the fruit of the domesticated Malus.