Technology has made its way into every facet of tennis, from what you eat to the gear you use  to how you train. There are apps and devices to help you select proper foods, monitor your miles and heart rate, strokes and serve speed. Fitness training is one of the biggest app categories out there of course because fitness is critical to success in every sport (AND healthy is trending). In the past, tennis players looking for something specific to their game have had to settle for a tennis program within a larger one.