tap the side of the phone, it responds to accelerometer sensor.

which reminds me of building breadboard RF sensors (using fixed caps with variable for calibrating parasitic capacitance) and since these are just oscillators you can calibrate a beat frequency (heterodyne mix) in audible range that has the theremin timbre of a squarish sine wave that you can plug straight to a speaker

It seems to make the user dance, would fun to see video of people using it for the first time. haha