One app I've found rather useful on my iPad is called Ubersense, and it's free. It allows you to film yourself and then group videos by element and person (skater or coach, for example), and watch the videos in regular speed, slow-motion, or even scroll through the video at your own pace (forward or backward, to find the motion of interest, for example a free leg coming through). You can also record your coach's comments over the video, draw on a frame, or show 2 videos simultaneously, either side-by-side or overlapped. You can set different start points for the videos to make sure the elements are synchronized, too. Overall, a great app, and it's free so no complaints! You need to register for some features but that's also free and they send very few emails.