programming abstractions ? SAGA and Cactus ? that facilitate the development of applications for distributed infrastructure. SAGA provides a high-level programming interface to Gridfunctionality; Cactus is an extensible, component based framework for scientific applications. We show how SAGA can be integrated with Cactus to develop simple, useful and easily extensible applications that can be deployed on a wide variety of distributed infrastructure, independent of the details of the resources. Our model application can gather and analyze network performance data and migrate across heterogeneous resources. We outline the architecture of our application and discuss how it imparts important features required of eScience applications. As a proof-of-concept, we present details of the successful deployment of our application over distinct and heterogeneous Grids and present the network performance data gathered. We also discuss several interesting use cases for such an application ? which can be used either as stand-alone network diagnostic agent, or in conjunction with more complex scientific applications.