In this paper we present the design and implementation of RVision (Remote Vision), an open architecture, high configurable tool for cluster monitoring. We focus on the description of it's modular architecture, emphasizing the new concepts we are introducing for cluster monitoring, such as monitoring sessions and the support for dynamic linking of monitoring libraries. In addition, we measure intrusion with several benchmarks and applications under different scenarios. RVision distinguishes itself from other available tools for cluster monitoring because of its open architecture, high configurability, and low intrusion. It is being used in production mode, in our research center, and has proven itself as a powerful alternative for cluster monitoring, especially in heterogeneous clusters and cluster of clusters.