WISER is a scalable network emulation tool for networks with several hundred heterogeneous wireless nodes. It provides high-fidelity network modeling, exchanges packets in real-time, and faithfully captures the complex interactions among network entities. WISER runs on inexpensive COTS platforms and represents multiple full network stacks, one for each individual virtual node. It supports a flexible open source router platform (XORP) to implement routing protocol stacks. WISER offers wireless MAC emulation capabilities for different types of links, waveforms, radio devices, etc. We present experiments to demonstrate WISER's capabilities enabling a new paradigm for performance evaluation of mobile sensor and ad-hoc networks.