Location awareness is an important capability for a series of wirelessly-enhanced business and consumer mobile applications. Low-cost devices that can be incorporated into a broad range of business and consumer appliances can be used for location determination and tracking. In this paper, we demonstrate a radio beacon-based approach that suggests heterogeneous wireless networks can be joined together to provide wide area tracking capability. Our implementation is based on probabilistic and statistical techniques, where signal strengths measurements from cellular networks are used to estimate the user's location. Simulation results and field tests around Lancaster University campus show that these techniques can achieve good performance (accuracy less than 50 m) compared with traditional deterministic methods (i.e. triangulation).