Talking Tape. Rub your thumb nail along the ridges and listen to the message. Five different messages (‘congratulations’, ‘happy birthday’, etc) and 20 tapes to a pack for $19.58 (£9.99).
One method is to hold one end of the strip between your teeth. Then, when you run your nail along the strip you hear it talk, but no-one else does. Or you can stick one end of the strip to an inflated balloon or a paper cup using sticky tape. The balloon or cup acts as an amplifier, and you can then demonstrate it to anyone nearby. Never heard a balloon talk? You have now!
I’ve always thought that this would be a great idea for the rumble strips on the side of highways. Not that the current rumble strips aren’t jarring enough, but think how much more effective it would be if your car started booming “WAKE UP! WAKE UP!”.