I just did this last week when I was trying to detect the location of a brake line leak on my F/S Dmax,.... I could see the wet spot, but could not specify where the pin hole was,... set up my phone, press record,..pushed brake pedal,..hit replay,..voila!
I actually use the camera as a mirror of sorts because you can never see where the bolt goes when working on the boats... haven't had to do anything on the truck that really needed this yet...