S. Benford, C. Magerkurth, and P. Ljungstrand. Bridging the physical and digital in pervasive gaming. Communications of the ACM, 48(3):54–57, March 2005. [url]
This article contains a good review of pervasive games. It also describe the current advantages and limits of technological implementations like: dealing with uncertainty; hybrid architectures (reconciling client-server and peer-to-peer); hefting domains (which elements to represent virtually); multiple locations configurations; orchestration of real-time management and live-games.