How about a Garmin 305 or 500 strapped to a ROK or sled. They are accurate within a few feet now and will show how many feet (miles?) a kite has moved as well as elevation change.
Or you can strap your Android phone to it, it'll do it too.
There are also dozens of apps tthat function as Pedometers, route diaries, speedometers, acceleration meters, heart rate monitors etc. More info then anybody wants.