Interesting point Dave!

There are also phone apps that can text your position with a time stamp too.

Another option for timing the finishes without having to stay up all night is to setup a camera in view of the "official clock" and the finish line with a light to illuminate sail numbers. Sailors also record their finish times in a log book that can be used to cross reference the camera data (or resolve issues like multiple boats finishing simultaneously with sail numbers obscured).

My contour camera can go easily for 12 hours with a power supply...then you scroll through the video matching the log book entries with the video clock to get the official finishes.