“This is a, well, tiny FM transmitter that can have various applications both probably legal (pirate radio, your own low-power radio station…) as well as the undoubtedly illegal (FM jammer, spy bug…). The choice is yours!
It can run on a voltage between 3 and 13 volts, draws 2-3 milliamps and has a theoretical output power of ~3 milliamps (although you could easily add an RF amplifier).”