llamalicious's Journal: Rejected: HOW-TO: build an RF homing beacon, ala RFID

I submitted this a while ago for ask slashdot, so I figured I'd post it here, in case anyone who reads my journal might be an electronics geek/guru:

I'm a budding electronics geek, trying to build what amounts to an RFID tag and scanner system to act as a homing beacon, but without the unique ID data. I'm looking to have the tag/transmitter be powered by magnetic field generated in an antenna on the device, with the scanner/tracker sending out the signal. An optimal design would include a return frequency differing from the input, very tiny size/mass and a range of up to 50 feet. So far I've been stumped trying to find good information on the internet about how to build my own, so I'm asking all you /. electronics geeks: What are some good resources to check (online, books, schematics)?