We present a new simulation toolkit called TRAILS (Toolkit for Realism and Adaptivity In Large-scale Simulations), which extends the ns-2 simulator by adding important functionality and optimizing certain critical simulator operations. The added features provide the tools to study wireless networks of high dynamics. TRAILS facilitates the implementation of advanced mobility patterns, obstacle presence and disaster scenarios, and failures injection that can dynamically change throughout the execution of the simulation.??Moreover, we define a set of utilities that enhance the use of ns-2. This functionality is implemented in a simple and flexible architecture, that follows design patterns, object oriented and generic programming principles, maintaining a proper balance between reusability, extendability and ease of use. We evaluate the performance of TRAILS and show that it offers significant speed-ups regarding the execution time of ns-2 in certain important, common wireless settings. Our results also show that this is achieved with minimum overhead in terms of memory usage.