I have always thought that wrist or sleeve mounted GPS gear could add a lot to skydiving safety. Just knowing ground speed on jump run would be invaluable for figuring out how long to wait between exits. I once did a sunset jump where fog formed during the freefall. It was zero zero visibility until I broke out at about 100 ft AGL, fortunately over a clear landing area. Sure would have liked a GPS telling me where the DZ was. One more thing, couldn't you use GPS to figure wind direction and speed by doing a contant rate full circle and looking at ground speed variation at different headings? Might take some software to make it easy, but why wouldnt it work?