I'm not much of a tennis player, so I don't know if this is a great idea or not. But one of the many reasons I don't play a lot of tennis is that I don't enjoy stooping over to pick up the ball a few hundred times per match.
Kim Seunghyun and Yu Yunjo's Tennis Picker is a Velcro strip that you can tape to the head part of your tennis racket. To pick up a ball, just push the Velcro against it. Seems like you could make your own pretty easily by attaching a strip of hook Velcro to a racket.