Philips has patented a system allowing collecting card to control a toy or game by playing a special tune.

On the front of the cards, there would be a picture of superhero or a game character. A wafer-thin sound chip inside the card could be activated with a squeeze. The song or sounds generated by the card would then be picked up by a sensor inside a compatible toy, triggering a response. A doll could dance in time with the card’s music, for example, or a knight could wield its sword in response to a roar.

The sound emitted by a card could even trigger a pocket computer game, perhaps unlocking secret features for the player.

Via New Scientist.