These are a great stocking stuffer for kids and grownups alike, particularly those with an affection for the "Retro" craze. Since these come on a keychain, they're easily attached to backpacks or... keys, making them portable and easily accessed. The electronics are simple, and a fun way to pass the time while thinking about just how far the world has come in the past 40 years. After all, the original Mattel Electronics were essentially among the world's first true hand-held games.
With a suggested retail of around $10, you can find these at major retailers like Walmart and Target, but keep in mind that certain ones might be hard to find, and thus third-party sellers will be listing them on Amazon and the like, usually at a higher prices.