And you thought wearables only applied to your wrist.

Between a bevy of 4K television announcements at CES 2014, Sony announced a whacky Tennis Sensor that can help improve your swing.

It simply latches on to the bottom of your tennis racket, almost inconspicuously, to stream data to your smartphone over Bluetooth. An app will tell you how fast the ball is travelling thanks to vibration and motion sensors, what kind of swing you performed, the amount of spin you applied to the ball, and a breakdown of the performance of your swing.

For now, Sony's Tennis Sensor is a concept and won't be on sale anytime soon. But it leads the way for future gadgets in an era where even your tennis racket has become "smart".