It's bad enough to have your phone's “movements” tracked. Unfortunately putting it in an anti-stat bag also keeps it from receiving calls and almost everything else it's supposed to do for you.
OTOH your FasTrak/FastPass transponder is doing the same thing and all you need it to be exposed for is when you pass through a toll facility. So we keep ours in a “bag” and just throw it up on the dash when we cross a bridge here in the SF Bay Area. It is bad enough for Google to be tracking you, but for us, it is unacceptable for the State of California to be doing it too. Now, with transponders and the phalanx of cameras we are under 24/7 “surveillance” supposedly for our own good. The only thing they can't do yet is smell us, but I am sure that they're working on that as we speak. When that happens, they will instantly know where every illegal alien Mexican is. They will just have to follow the frijoles!