I hate that noise! You know, when you’re playing music in your car on your iPhone or what have you, an all of a sudden that weird syncopated buzz comes out of nowhere? I understand it’s the high-powered command/location signal GSM phones do regularly to ping local towers. So you don’t want it to stop, you just want it to stop making that noise. These Buzz Killers are, as far as I can see, just little radiation-blocking cards that you can set your phone on so it doesn’t blast your audio system with that signal.
Could you do the same thing with a couple pieces of foil, or a bit of scrap metal? Probably. Why not give it a shot? Or you could just pay the $7.50 for a card, which is probably guaranteed and will never be mistaken for a piece of trash you left on your desk.