Until now, any tennis swing sensor was a bug or sticker players had to attach to their racquet, sometimes negatively affecting how the racquet plays, which is why the Babolat Play is so impressive. The French company worked closely with sensor company Movea to integrate an accelerometer- and gyroscope-equipped circuit board into their popular Pure Drive model without affecting its playability a tick. The resulting smart racquet has identical specs to the original, right down to its 300 gram heft. Here’s how it works.