I took my towed underwater mount GoPro out today and drug it around behind a kayak for a couple of hours. The whole system is still in development, but one of the things it would be nice to do is be able to overlay certain text information onto the video. I assume at some point I'll be using some sort of USB camera hooked to a computer in place of the GoPro and I would like to be able to have it display things like current position and depth on the screen. These would be collected by an attached GPS and USB depthfinder, but I don't know how to meld them into the video feed. Ideally it would act like a subtitle that is recorded kind of like metadata and can be turned on and off.