Although from 2008 I have only come across a PDF of it again recently. The paper covers designing a location-aware augmented reality game and includes some concepts that may be useful for others. It won best paper at MobileHCI 2008.
Braun, A, Herbst, I., Broll, W., and McCall R. TimeWarp: interactive time travel with a mobile mixed reality game. In the Proceedings of Mobile HCI 2008. Amsterdam, Netherlands (Best paper award)
Mobile location-aware applications have become quite popular
across a range of new areas such as pervasive games and mobile
edutainment applications. However it is only recently, that
approaches have been presented which combine gaming and
education with mobile Augmented Reality systems. However they
typically lack a close crossmedia integration of the surroundings,
and often annotate or extend the environment rather than
modifying and altering it.
In this paper we present a mobile outdoor mixed reality game for
exploring the history of a city in the spatial and the temporal
dimension. We introduce the design and concept of the game and
present a universal mechanism to define and setup multi-modal
user interfaces for the game challenges. Finally we discuss the
results of the user tests