A project from the Troika art and design collective. Snip from description:
The SMS Guerilla Projector is a home made, fully functioning device that enables the user to project text based SMS messages in public spaces, in streets, onto people, inside cinemas, shops, houses… Small, portable, and battery operated, the SMS Guerilla Projector contains a mobile phone which enables the device to receive and project messages from other people.
Link (via placebokatz blog post, thanks Susannah Breslin)