It allows players varying in skill levels to practice to be better at both tennis and cycling. The launcher is towed to the court on its built-in bicycle trailer. A bike is secured to it and functions to drive the device. Pedaling the cycle as one would on a trainer drives the two launcher wheels. The cyclist then aims using the bike handlebars to and pulls the lever to launch balls to the hitter.
Check out the High Speed Videos (Slow Motion) at 300fps and 600fps of the launcher in action, and other information about the launcher and it's construction:
Construction Detail Video: