I've been teaching tennis for almost 50 years! WOW! This has been fun! What's the biggest change? The smart phone! Not sure how I got by for so many years without it.
I can show immediate videos of any stroke, serve, etc. I can show them a video of how to stroke correctly, then take a video of them performing the same stroke for instant gratification and critique. The slow-motion feature is unbelievable. I don't need a bulky video camera and a stand for it. I just pull my phone out of my pocket and return it when I am finished. Also, I can send my students the video for reference anytime. All of my students are completely technically gifted. They really like the benefits of using the smart phone.
There is really no reason for a young tennis player having poor form on any stroke or shot.
What a great tool.
Have fun on the courts!