Here is some of the gear I’m using for flight training (and recording the flights):
The first video I shot was on my iPhone XS Max using Filmic Pro (video app) and placing the phone in a suction cup mount on the back windshield of the Cessna. The audio was pulled directly from my Bose A20 headphones via bluetooth so it seemed pretty easy for setup and recording. The only drawback was that the angle was too low for my liking and I could only hear myself on the audio (not my instructor). I tried mounting the suction cup with phone on the front windshield but the vibration was so bad that the video was unwatchable.
Now I have the GoPro HERO 7 Black (which has built-in stability and vibration stabilizer) and it can safely sit in the suction cup mount on the front windshield. I’ve also added the cable adapter which pulls in the audio from everyone in the cockpit so it records clean audio along with the smooth video.