It has been done. $6.95
http://www.amazon.com/Crime-Scene-Mobile-Phone-Blocking/dp/B00AIJ9OYG/ref=sr_1_1/181-3246688-6713456?ie=UTF8&qid=1375557253&sr=8-1&keywords=faraday+cages
:( -- A day late and a dollar short, as always.