An anti-static bag (even the metallized type) probably won't be the best idea. Faraday cages depend on the conductivity of the outer shield to exclude electric fields from the inside, but anti-static bags aren't very conductive (100k-10G ohm square resistivity[1]).
You might even be better off wrapping the phone in aluminium foil, but the problem is then going to be ensuring that all seams in the "cage" are actually conductive.
You might even be better off wrapping the phone in aluminium foil, but the problem is then going to be ensuring that all seams in the "cage" are actually conductive.
[1]http://www.esdjournal.com/techpapr/ryne/esdbags.htm