If you're on an iPhone and a mac, plug your phone in and open QuickTime player on your computer. Make a new file and select the source as the iPhone. That will record your phone's screen. Press play on the phone to start playback, make sure the screen doesn't time out and turn off.
What I'd love to see is an app that automatically syncs up video from the flight with the flight log. It would be great if the cached video on the phone recorded the whole flight, not just when you press record, and could automatically be displayed alongside the flight log.
iPhone 6S