We provide evidence of the feasibility and effectiveness of a middleware architecture for mobile devices which employs dense distributions of small computerized entities for providing fault-tolerant location-aware services. We do so by describing exemplary implementations based on radio frequency identification (RFID) as an enabling technology. Firstly, we present prototypical implementations of the hardware abstraction layer and of selected core middleware services. The latter enable a mobile

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... evice to store and retrieve data and position information in physical places in a fault-tolerant manner, and to identify places based on a location abstraction which is robust against failure of individual tags. Secondly, we investigate the feasibility of some higher-level services and applications by developing and evaluating prototypical systems for tracing and tracking, self-positioning, and collaborative map-making.