This paper presents an architecture for location aware applications, where positioning sources such as GPS, WaveLAN and Bluetooth devices can be seamlessly interchanged and combined to achieve a more accurate positioning service with a higher availability. The architecture also supports peer-to-peer communication to allow clients to interchange position information over a network such as Bluetooth or WaveLAN. This enables a user to use other users position sources if their clients are close enough. The position information can be used directly by an application or be combined with habitual and other contextual information to achieve more personalized applications. A generic positioning protocol for interchange of position information between position sources and client applications, and different techniques for merging of position information are presented. The interfaces to the platform are also discussed. The paper finally touches on privacy issues and outlines a schema for handling positioning information by user controlled contracts.