This document discusses a data fusion technique to improve the accuracy of wireless ranging. It analyzes the performance limitations of using received signal strength (RSS) and two-way time-of-flight (ToF) measurements individually for ranging. The paper then proposes an algorithm to combine RSS and ToF measurements to improve ranging accuracy. Testing of a prototype using off-the-shelf components showed the approach improved accuracy over individual techniques, though was not precise enough for fine-grained indoor positioning. The method could support applications like hazard detection and is suitable for integration into low-cost wireless modules.