We present the SS7Box modular signaling platform, a tool for rapid application prototyping in a cellular mobile network, and examine in detail its performance limits for the application of active network-based tracking, called SS7Tracker. This application is a highly configurable, non-intrusive and cost-effective solution for large-scale data collection on user mobility in the network, uniquely enabling tracking of both active and passive mobile clients. We present performance studies of real deployment in an existing cellular network and document the measured as well as simulated performance limits such as platform interconnection utilization. Other factors, such as impact on battery consumption of the tracked device, are studied as well. Platform modularity and variability is discussed and demonstrated by further deployed use cases. We conclude by observing promising applicability for future cellular networks.