Using green screens (chroma keying) is a popular option for videographers to create unique backgrounds for their videos. Currently, there is not a way to do green screening from inside the app itself. However, there are options for third-party apps that can be used on iPhones or iPads. You can then use screensharing to get the green screen camera angle into Switcher Studio.
We highly recommend the app, VeeScope. To use VeeScope with Switcher Studio:
Open the VeeScope app, and position the camera on your subject with the green screen behind them.
Next, use iOS screensharing to share your iOS device's screen inside of Switcher Studio.
The complete process will be Green Screen App (iOS device) -> iOS Screensharing -> Switcher Studio.