Mobile devices with wireless communication capabilities are a constant in our daily lives. This offers the possibility for such devices to exchange information for their users to assist in their daily lives. Consider for instance the exchange of information about points of interest in the locations that the user usually frequents. One should expect those devices to support such an application in a decentralized fashion, through pair wise interactions, without the interaction of the user, and avoiding to disclose information that might be sensitive to a central entity. Current solutions are not suitable for supporting such applications since most rely on some kind of centralized architecture (either brokers or rendezvous nodes), other solutions that don't rely on centralized solutions present a high overhead. To address this challenge, in this paper we propose MobUser, a novel topic-based publish-subscribe service specially tailored for supporting location-aware operation for mobile devices in a decentralized fashion. Extensive experimental work shows that MobUser offers not only better performance but also superior delivery rates when compared with a state-of-the-art mobile publish subscribe solution. We also show through a prototype implementation deployed on Android 4.0 devices, that the overhead and energy consumption of MobUser is acceptably low.