"The "Brief Safe" is an innovative diversion safe that can secure your cash, documents, and other small valuables from inquisitive eyes and thieving hands, both at home and when you’re traveling. Items can be hidden right under their noses with these specially-designed briefs which contain a fly-accessed 4" x 10" secret compartment with Velcro closure and "special markings" on the lower rear portion. Leave the "Brief Safe" in plain view in your laundry basket or washing machine at home, or in your suitcase in a hotel room – even the most hardened burgler or most curious snoop will "skid" to a screeching halt as soon as they see them. (Wouldn’t you?) Made in USA. One size. Color: white (and brown)."
This product uses two principles to deceive the potential thief. One, a robber wouldn’t think that a pair of underwear would have a secret compartment to hide valuables. Two, a robber would never think to pick up a pair of dirty poop-stained underwear.
I suppose this type of thing would work to deter a thief, but if anyone else saw this thing lying around your home or hotel, what would it say about you? And where do you put it so your valuables aren’t just lying around in the laundry basket or in your suitcase? It’s likely more people buy this as a gag gift, so they have an excuse to gross out the recipient with a pair of fake dirty underwear: "No, but look, you can hide your valuables in here!"
(Although this does make me wonder: where else is this concealment principle used, to hide something valuable with something disgusting?)