I recently discovered an amazing app for the iPhone and my Apple Watch. It is called Swing Tennis and it will track all of your shots during a tennis match. It does this automatically, using the accelerometer to track the type of shot and spin you use. It is pretty amazing.
You can input some specific information while you play a match, tracking the score and faults for serving very easily. There is some additional tracking such as unforced errors, etc. if you want to track it, but I have not felt that was necessary at this point.
One of my favorite apps at the moment.