Rashid O., Mullins I., Coulton P., and Edwards R. “Extending Cyberspace: Location Based Games Using Cellular Phones,” ACM Computers in Entertainment, Vol 4, Issue 1, January, 2006 This article is a comprehensive overview of location-based games, describing enabling technologies as well as examples of what's out there (no mention of Catchbob! :( maybe it's because designing our game was not the ending goal but a way to study certain phenomenons ). As they describe, it seems that GPS and WiFi are the most used technologies and they describe how bluetooth and RFID might be a good contribution.
Interestingly, the article gives a good critique of existing gameplay:
All the location-based games discussed can be categorized into three genres: action/adventure, treasure hunt, and role-playing games. Finding other players in a shoot-em-up game can initially be exciting, but the gameplay can quickly become repetitive, and the games rely on high numbers of players with the same game in the same area. Treasure hunt games can quickly become boring when played alone, and those that create an event appear to receive greater publicity and recognition. Although some of the games being marketed are massive multiplayer online role-playing games (MMORPG), their inability to compensate for the short gameplay of cellular users may hamper the ability to immerse players in the games. Geo-fencing provides a new element to games, in that players can specify their own virtual territory based on their actual physical neighborhoods. The incorporation of community features such as mobile chat are effective because they take advantage of the social nature of the cellular phone, and are features likely to prove significant in the success of these games. (...) For now, location-based cellular gaming is a niche market, which often depends on players owning specific devices and subscribing to specific carriers. However, there is strong evidence that these games are capturing the imagination of a new audience, and if the games can mature to give a wider variety of gameplay and experience, they might yet achieve their potential as a major location-based service.
Why do I blog this? it's a good overview, it depicts the actual picture of location-based games and some of the challenges. I would maybe add that lbg should go beyond object collection/hunt (in the same way LBS should move forward buddy finder and place annotation) to be more successful, offering more interesting challenges. But hey that's not so easy. Maybe a good way to do so is to have more features based on these scenarios or to radically invent new approaches.
Also, see the expression "extending cyberspace", this concept is still around for some people Alex!