There is no way to get 1080p and higher resolutions, to be saved to your device, over-the-air (RF)!
DJI has that option for pictures because file size is so much smaller (easier to wirelessly transfer) than video.
As another person mentioned, Video shot from your AC, can be cached to your device, in near realtime, by turning on 'video caching' within the Fly app on your device. This is a good option if your wanting a simple method of rough overview of what you just shot ("Was that any good, should I shoot it again" That kind of thing)
(Using this cache function will only save an approx 720p resolution copy of your video, on your device, and only after you have ended that recording and allowed a few seconds for it to save internally.)
There is a download function, via the file view area of app, that transfers individual files over wireless, but its time consuming and battery draining, so best not to use that method unless you have an extra battery that your not going to be flying (and WHO would do such a strange thing, right!)
I thought I'd add this just in case, as I once asked your same question.
In order to have footage thats saved on my device, I decided to start screen recording. This was mostly in case of a flyaway or crash, so I could have a place to start in search and for evidence. Luckily, havent needed to use it for that, but now I quite like having a corresponding copy of video that has all the telemetry info, as Im into the flying aspect, not just the footage... My Mavic 2 supports 1080p FPV on screen, so I can record that, at 1080p and get a resulting video res thats just below true 1080p, as long as I keep a good solid RF signal with M2!
Keep in mind, this will record all of the on-screen telemetry, but I believe you can swipe your finger up on screen and it'll hide everything except the camera view from screen? Mine is good enough that I dont need my SD card footage alot of the time, but thats only for personal SOOC shooting, where I wont be editing anything and there wont be 3rd party oversight.
Just a thought. I use AZ Screen Rec on android. iOS may be different!
So to summarize;
- If you just want a lower res copy of your SD card footage to view briefly while in flight, in order to determine if you need to re-shoot, etc... Then CACHING is for you.
- If your looking for a resolution thats just below 1080p (if your Fly app supports a 1080p FPV from MM), that will help you avoid messing with the SD card and the Computer, then I'd say try a Screen Recorder?
I hope I didn't add too much info and I hope some of it helps you!