This little device can serve as a Persistence of View (PoV) display. Just make it swing in the air and it will display a message.
To program the ATtiny85 you may follow this guide: http://highlowtech.org/?p=1706
pocketPoV and its surrounding materials are published under CC BY-SA 4.0
pocketPoV was designed by RS & CBS for Telecom Electronics Association AETEL, based at the Campus Sur of Universidad Politécnica de Madrid.