Dig through YouTube's sands, and you'll find this: An HP concept video from 2007 about an augmented reality game called Roku's Revenge. (No, not that Roku.) It looks like fun. A lot of fun. So what ever happened to it?
It was part of a project called MediaScape, or Mscape, a gaming platform that HP showed off as the future of location-aware gaming. MScape actually worked, at least in a handful of demos shown on iPaq devices. It eventually made its way into a beta product for Windows Mobile.
Since it was developed by HP's U.K. division using funding from the British government, most of the "mediascapes" that have been created so far have been in the U.K. There was even a meetup as late as December 2008, though since then the project seems to have gone cold.
Several influential companies have put forth competing ideas about how AR will develop--some good, some not so good. But for all the challenges that stand between developers and reality, gaming has perhaps the least; its information-stream doesn't need depth or historical awareness, just a sense of location relative to other players. Perhaps we'll see someone pick up where HP left off.