This paper presents a robotic platform which is targeted to perform the task of a tennis ball boy. This platform is self-contained with on-board sensing and computation, uses only cost-effective off-the-shelf components, and was designed to perform robustly and repeatably in semistructured real-world environments. In particular, this paper presents a particle-filter implementation that allows the robot to localize itself and navigate on a tennis court. Along with navigation and tennis ball detection, this will enable it to pick up tennis balls on a real tennis court. This paper describes our system, presents our initial experimental results, and discusses some of the challenges faced.