The Theremin I/O app was developed by Johan Nordberg and Giosuè Russo.
This special app allows you to turn your iPhone camera into a touchless musical instrument. Incorporating your smartphone's camera and flash, Theremin I/O offers a completely new experience to generate musical melodies and sound. It functions by way of utilizing the camera to measure the density of light reflected off from your hand. The signal then passes onto the synthesizer, creating the musical tone. The Theremin has eight preset sounds that allows you to create a large range of sounds. For those of you who aren't Theremin natives, do not worry! The presence of a harmony quantizer scales the frequency to a solid musical note.
For professional Theremin users, you can use Theremin I/O with the MIDI upgrade to use as a digital controller.