In this case its software that treats the iphone as a camera of their own. Looking at the screenshots, the UI/UX is extremely similar to current blackmagic cinema cameras. So you can have two camera operators, or the iphone on a tripod or whatever, and each camera operator will know which settings their camera has and to typically match both the film cameras. Like a quick visual check that both cameras are at the same shutter speed or shutter angle, resolution, white balance and tint, and having the same style of histogram so they can match exposure on both cameras.

Its actually fairly neat and cool that they put time and money into this app to further their ecosystem. I guess theres a large overlap of people that film with iphones and also want to buy a legitimately good, budget cinema camera in the pocket 4k/6k.

I don't know HN's opinion of blackmagic, but they do some pretty cool stuff. With the purchase of a camera they include Davinci Resolve which is a fully featured Adobe Premier Pro rival. For reference premier pro is $21 a month, and the cheapest blackmagic cinema cam is the pocket 4k which comes in at $1200, after 5 years you have a free camera (thats still actively updated) if you consider Resolve to be equivalent to Premier Pro. Also they've constantly pushed the industry to be more affordable. They were pretty much the first that let you use a consumer usb c SSD to record raw formats. When the camera released, you could get 1tb samsung T5's for around $100, while one of their rivals RED cameras made you purchase a proprietary SSD that still costs $1500 for 480GB. Also in terms of affordability, it wasn't unheard of for a cinema camera to charge thousands of dollars to be able to use a cinemaDNG raw or ProRes, yet blackmagic cameras came with multiple raw recording options for free.