I love the sounds PLU Collective is getting out of this "Diddley Bow" made from a branch. He's using a lot of apps to achieve it. At the end of the video there's an example of how it sounds sans apps.
A homemade electric diddley bow with a single pickup made from the windings of a wall wart DC to AC transformer with a magnet, a wooden box body, an elm branch neck, a guitar machine gear, and an electric guitar string. The electrical signal from the vibrating string is routed into the iPad using a 1/8” TRRS cable which shows up as the built-in headset microphone input in AUM after going through a passive circuit ( http://www.ltdan.de/images/dPLUG.pdf ) housed in an Altoid tin box with an audio taper potentiometer (brown knob) used to eliminate electrical noise in the output signal from the diddley bow plugged in with a standard 1/4” mono guitar cable. In AUM the signal is routed through various apps before being output to the headphones connected to the 1/4” stereo output jack on the Altoid tin so you can monitor your playing and hear the audio output from the iPad.