My friend Timo mentioned that GoPro Hero 3 can connect to your phone with some lag. This opens me an opportunity to get immediate feedback about my tennis serving with topspin. I want to train serving with topspin and I would like to see how the shot looks from the side. Basically, attach the camera to the net and look the shot with your phone/monitor (probably in the future in Google glasses or something like that). Little lag does not matter here, it just need to be fast enough not to be irritating. I currently use the iPhone 5 camera for the analysis but hard to see the ball's path and very slow method.


![enter image description here][1]


**Is there any device to help in analysing serving with topspin from the side?**


  [1]: https://i.sstatic.net/dqN0R.png