Anti-theft lunch bags. Here is the description:
…a few spots of mold may work wonders to protect your precious sandwich when your custom labels, pleading requests and desperate detective work fail to find your regular at-work lunch thief. Reusable, resealable, one-size-fits-all and ready to go right out of the box (or brown paper bag), these clever little containers from Think of The might seem more like a prank object or gag toy than a functional product but it will almost certainly deter even the hungriest of would-be food hackers.
For the pointer I thank Lawrence Rothfield, author of this excellent book.