One of the best teaching aids of the last couple of years is smart phone and tablet video technology. In my smart phone, iphone 4S and tablet, Ipad, I have a video camera and a swing analysis software app that not only allows me to show my pupils their swing in slow-motion & frame-by-frame playback. I can also make side by side comparisons, use multi-colour drawing tools and send them, directly from the practice ground, via email the swing video and a voice memo of the lesson, simply unbelievable!
After having tried several apps I currently use the V1 app which I believe to be the best on the market. If however you know of any other app that is better please let me know.