Camo
Used by 2 peoplereincubate.com ↗
“As for video, I occasionally use Reincubate's Camo to turn my iPhone into a webcam.”
Stilgherrian Interview, Journalist, podcaster, media producer · via Uses This 
“It's connected to the Mac via lightning and in conjunction with the fantastic Reincubate Camo app, which provides a driver so that macOS treats it as a normal camera input.”
Justin Searls Interview, Programmer · via Uses This