On NPR this morning I read this article entitled Texting Underground Can Save Lives and Caves
. Sixteen year old Alexander Kendrick won the 2009 International Science Fair for inventing an extremely low frequency cave texting device. It's described as something like a "computer attached to a ham radio", transmitting data using low-frequency radio waves that can penetrate rock more easily than high-frequency transmissions like those in FM broadcasts.
Unfortunately it doesn't appear Alexander is an amateur radio operator as I couldn't find a license database entry. I'm curious as to the modulation he is using; this would be an ideal application for PSK and one could use existing amateur radio software.
Kudos to Alexander (PSSSST! You can connect a computer to a ham radio! Email me! :-)