Matt Mets @ MAKE writes:

Here’s an older project by Micah Dowty, that I just found out about: a homebrew soft circuit RFID tag. Not content to just make a homebrew RFID reader using a Propeller microcontroller, he proceeded to design an RFID tag using only an ATtiny85 microcontroller and an inductor, and built an antenna for it using conductive thread. The result: a completely homebrew RFID setup, which is compatible with EM4102-style RFID tags. Awesome!

An RFID tag is a passive (non-powered, in most cases) electronic device that stores information. It’s how all those touch-based payment systems work. They’re in your credit cards, passports, office key fobs, and are used as security devices on retail products. What’s remarkable about this one is that it’s actually embedded into the fabric, since the information is stored on the tiny chip, and the antenna, required to transmit the signal to the reader circuit, is sewn from conductive thread.