There is a long list of exotic James Bond gadgets used in his movies but none of them is small enough to fit in a hollowed coin except for a set of faked fingerprints or a microchip with a lot of information. However, I don’t think you will ever need one such coin unless you want to add it to your collectibles. Just keep it in a safe place or one day little Johnny may be short of a quarter and run after the ice-cream truck with your valued possession; that would be a very expensive ice-cream.
The Hollowed coin costs around $30.