IntelliTours

Found this via Engadget, although apparently it has actually been around for a long time:

IntelliTours creates audio and multimedia tours that are guided and triggered by GPS navigation. The tours work outdoors anywhere in the world. The tours are packaged for handheld walking tours, auto and RV trips, and fixed-route tourist trolleys, buses and trains.

It seems that there are already lots of existing location-based tourism applications on offer all around the world - there just isn't much academic research/theory on the matter, nor is there an aggregated account of their successes/failures. I guess this is where my thesis can come in! =)