Your iPhone is very capable of capturing amazing video. With a decent smartphone filmmaking rig, you can attach your lights and other accessories to record more professional videos. The Sandmarc Film Rig fits the bill. It lets you mount your iPhone, GoPro, or a small mirrorless camera. It has a lightweight aluminum construction, weighing only 13oz.
The Sandmarc Film Rig is compatible with a wide variety of iPhones, including the iPhone 13 Pro Max. It also supports Android phones under 4 inches wide. It has a waterproof design. You can find out more about it here.