Just found this interesting classification of locative media on Brian Degger's weblog. It's part of a talk he gave at ISEA2008:

Why do I blog this? currently writing a book (in french though) about locative media, I am gathering some updates about locative media classification. Some interesting elements in that table, especially the broad definition of locative media, now considering broader range of participants (non-humans such as pigeons) and clearly beyond boring pizzeria-recommendation applications.