A few months ago I picked up on the fact that although I was showing people their mistakes and they would correct them if I moved them during that session, it seemed to quickly fizzle out and they'd go back to doing it their old way. Then I started using my iPad to film people doing poomsae and kicks and showed them on the video. After the first session I also bought an app called Coach's Eye (I've no business or personal relationship with them, just a happy customer) that allows you to frame-by-frame the action and annotate it with lines and arrows. This has been quite frankly great! I've had improvements in students after a single session videoing a few poomsae that would have taken weeks of nagging (don't forget you're doing X during this part) to get. Anyway, I don't know who out there is trying to make better use of technology during their instruction, but I thought I'd post a recommendation for this method (and that app).