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.

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