There is a big difference between playing tennis for fun and actually wanting to compete at events. You will need proper coaching to improve your skills. Courtmatics is developing a smart dampener that monitors your performances, helping you track how well you move. You will also be able to analyze your serves, ground strokes, and volleys thanks to this technology.
The Smart Dampener is also a fitness tracker, measuring your calories, steps, and distance as you work on the court. This Bluetooth device has a 4-hour battery life. It is compact enough not to get in your way. More info is available here.