Fourth generation mobile networks will allow end-users to roam over different network technologies, such as UMTS, CDMA2000 and Wi-Fi. These mobile networks make it possible to determine the location of the mobile terminal, which can be used by applications to provide enhanced services. Each mobile network technology has its specific way to determine the terminal’s location, and to provide this information to the end-user or mobile application. Mobile application developers should not be exposed to the peculiarities of the different network technologies, and should be offered a network technology independent API to obtain user location information. In this paper we propose an architecture that provides 3rd party mobile application developers with a secure API to obtain the user’s location over heterogeneous networks that are managed by different parties. The proposed architecture is validated by a proofof-concept implementation using UMTS and Wi-Fi networks.