Advances in mobile devices, sensors and wireless networks have motivated the development of contextaware applications. Such mobile applications use sensors for monitoring several features such as: location, temperature, velocity, weather, traffic jam, noise, air pollution, and so on. This monitoring enables service provision according to a given context. These applications are known as context-aware systems. Context-aware applications are sensible to user necessities, personalized according to his profile, requirements and context. They evaluate user environment and push information that is relevant to user context. In this paper we present Omnipresent, which is a service-oriented architecture for contextaware applications. Omnipresent may be accessed from either mobile devices or Web browsers, and it is based on Web services and well-established standards for LBS applications such as those proposed by the OpenGeoSpatial Consortium. Omnipresent offers several services: map presentation, routing, advertisement, and also works as a reminder tool.