Meet the Sweet Spot: a smart sensor that attaches to your golf club or tennis racquet and helps you take your game to the next level. It uses activity gaming to encourage physical fitness. Its mobile app (iOS/Android) has games to make practice fun. It has training games for both tennis and golf.
Sweet Spot is easy to install and remove. Just download its app, activate the sensor, and you are ready to start swinging. You can get it on Indiegogo.