A tool used by shoplifters. Usually a shoebox with one side of it cut out, and lined with tin foil. The missing side is held against the body and items are stuffed into the box and then walked out of the store. The tin foil is used so that the anti theft device won't set of any alarm systems on the way out. Often tested by putting a cellphone in the box and then trying to call it. If the phone doesn't ring, then it's usuable. If it does, the one solution is to use more tinfoil.
On a side note, you will be arrested if found in posession of one of these, even if you were not in the act of shoplifting.
Dude let's hit up Best Buy, I just made this sick booster box and they won't know what hit em.