So enter the Plug Mug. A mug, with a hole in it, which renders it completely useless to mug thieves. Just keep the plug safely stowed away from harm (on your key ring or in a vault) and you will find that no-one is interested in stealing your mug anymore.
This is where the old school glasses prove to be superior to the modern contact lenses. Brad Gressel has come up with Stix glasses concept where the arms are home to a pair of stainless steel tipped chopsticks.