The Casio I have will take video, so I tried recording a few patterns.  Works best if the wind is from a steady direction.  I know there can be problems with angles and such making the shapes look off, but it is great for seeing just how bad the intersections, tracking, and shapes can vary.  Works at least as well as a coach, especially if it's all you've got.  Using a tripod is a good idea.  Having a friend pan the camera around a maneuver doesn't really let you see what is going on.  Even if the plane flys out of the screen, say on the loops, you can see it come back in at the same spot and angle and know that the loops were at least consistent.

Still haven't figured how an 8 that looks perfect when you fly it can have two overlapping loops on screen.