Prodigy
The Lock-Cup is the perfect invention for the selfish guy who won't share his coffee mug.

As pictured here, it resembles an ordinary coffee mug, other than the hole on the side, which can only be sealed by the key holder.

This option might be suitable for the ultra-gourmet coffeehouses that keep losing mugs, or by office workers who are overly protective of their morning caffeine ritual.

Perhaps this product could be the next big thing in late-night infomercials?