go to accessibility and turn on voiceover when triple clicking on the power button. Turn your volume all the way down, start voiceover, go to camera, start respaming your video, then triple tap your screen with three fingers. This turns the screen off but it will still respam. Triple tap with three fingers to turn the screen back on. For extra security, you can turn on guided access after turning on voiceover, and disable volume buttons so it looks like your phone is completely dead unless someone triple taps the screen with three fingers.