I've used skydroid a few times and mapped one course myself. It is pretty good most of the time. There seems to be some lag with the gps info sometimes. But that may be the case with any of these apps.
I hadn't used any rangefinders in the past, and I frankly don't use it much. I just don't hit or control the ball consistently enough to worry about a few yards difference.
What I really need is a two-putt app.