haha good sir, the latency you are talking about has no significance to what you are trying to measure. if you see the start of the roll and end of the roll in your recorded video thats all you need to measure, how that video got to your phone doesn't matter at that point. I think you will find that measuring down to the 2 -3 milliseconds of inaccuracy in an iphone recording device is so imperceptible. I change my rates by 2-3 degrees per second sometimes and its honestly not even noticeable as you fly. some advice, I would start the roll going and then start recording on like your second or third loop, that way you avoid the speed up and slow down of your fingers on the sticks : ) cheers