The absolute best

I tried just about every GS app. Veescope is #1 for Live GS Video. It has the unique ability to use your B roll video WITH your prerecorded audio as your background piece. You can save these background videos for future playback within the App to use with your Live Video Recordings. Their are many settings for critical control: lock focus, exposure, & white balance. Adjust green screen color sensitivity and intensity. You can crop both Horz & Vert to eliminate any non keyed imagery. It even works with other IOS devices as a remote for recording, including Apple Watch! This is the must have ChromaKey App period!

Gogreenscreen about Veescope Green Screen Full, v6.4