Channel of communication and location-based services Seefeld blogged a relevant question he asked to usage watcher Stefana Broadbent at LIFT06:

After a data-rich and fascinating talk about the specialization of communication channels at LIFT yesterday someone asked if the introduction of position-information of your communication partner would alter the communication patterns. Stefana's suggested that there probably would be not much change in the pattern, since the 4-6 people that you do the bulk of synchronous and nearly synchronous communication with, you know well enough to know where they most probably are at any time anyway. Taking this further, these would of course be the same set of people that would probably give you the trust rating to expose their position. Thus, the question: Is there any market for all these mobile location based communication systems?

Not in the obvious implementation case. Maybe either by restricting types of locations, like Plazes does (which maps places I'm online, thus probably working and almost never my spare time) or by coming up with a system that is anonymous enough, but yet useful and not annoying (permission spam) so that you could extent the service to a much wider circle.

On the other hand, IM-style presence indicators (from "away" and "busy" to "phone", "meeting", "in the zone") potentially fulfill a much more important note in this context. Maybe phones start listening to things like how many voices (and at what volume?) there are in the room, how fast the typing-sound is, etc. They could at least switch to silent mode in this case? Hmm, how reliable could you detect that the owner is sitting in a movie or a talk? And why is there no "silence please" beacon installed in every cinema that mobile phones could pay attention to?