Also Blackmagic Camera runs on iPhone and can sync multiple sources (they don't give a limit, I imagine if you had more than 4 iPhone/iPads it could sync them a

Also Blackmagic Camera runs on iPhone and can sync multiple sources (they don't give a limit, I imagine if you had more than 4 iPhone/iPads it could sync them all). https://www.blackmagicdesign.com/products/blackmagiccamera https://www.blackmagicdesign.com/products/blackmagiccamera