The RH-03 Stereo Magnetic Field Sensor is a simple 9v powered circuit that uses two inductors to sense electromagnetic fields.  The PCB is custom designed, hand-wired and soldered, and mounted inside the hardwood case (available in a variety of different wood choices).

It's a great noisemaker, especially when paired with a stereo resonator, vocoder, or similar effects unit.  Wave it around electronic devices such as transformers, leds, cell phones, computers, or other devices to get a variety of different sonic textures.

It connects to any audio equipment via a 3.5mm stereo jack.