writes "Researchers at Harvard and Tufts University have developed a way to send coded messages without using electricity. David Walt, professor of chemistry at Tufts, and Harvard's George Whitesides have developed 'infofuses' that can transmit information simply by burning. The fuses — metallic salts depositing on a nitrocellulose strand — emit pulses of infrared and visible light of different colors whose sequence encodes information. They were developed in response to a call from the Defense Advanced Research Projects Agency for technologies to allow soldiers stranded without a power source to communicate. In the first demonstration of the idea, they used the infofuses to transmit the message look mom no electricity."
Currently the researchers are "trying to figure out a way to dynamically encode a message on the fly in the field without specialized equipment."