I use Race Chrono Pro, very similar to Harry's Lap Timer, but geared for Android on a Samsung Note 5 (stock camera) to record sessions and video. See the link below. I recommend turning the GPS settings to the most sensitive or buying an external Bluetooth GPS unit. There are features that allow you to overlay gopro/ external video with gauges. One final comment also buy a Bluetooth obd reader to get rpms and throttle position sensors to display in the video.
Sample video: