It's 3 years old but still very up-to-date from my point of view: Marko Athisaari's talk at Doors of Perception 7: here are few quotes I found relevant:

My topic is proximity. By proximity, I mean, quite simply, physical closeness; and many among you will ask, “How close is close?” But I mean the stuff that happens between the one-to-ten centimetres range and room-size interaction, and what people do, what kind of activities they undertake in that kind of space. (...) four kinds of services and product services value that people might get in physical closeness:

People in places: while we talk about devices being connected, and everything being connected in a technological sense, social interaction will be a prime driver in the future as well, even in technologically enhanced social interaction. By this, I don’t mean that we’ll supplant very good ways of communicating, like me speaking to you one-to-many now, but that other forms of communication overlay it – if there’s wireless coverage, you could be maybe discussing what I’m saying among yourselves. (...) he simplest and most important one, which has immediate implications and is quite near in the technological roadmap, is sharing different kinds of digital items, whether they’re personally created or otherwise, in physical closeness. We know from evidence in Japan where, for example, imaging phones have been around for quite a while, that across the table people won’t send the image across the cellular network, they prefer to show it on the device.

My things with me: We know that mobile portable products and appliances are very much linked to personal and intimate items, the kinds of things that one has an emotional relationship with. One can see that the relationship of people with their phone books is far from rational. (...) This includes not only items like a phone book or co-ordinates for other people in our social network, but also our personal and intimate media, like photographs. They need to be stored somewhere close by;

Enhanced Spaces: means content, digital content that’s local, related to this space, or the shopping environment. [the classical location based services postit like? nicolas]

Safe Consumption refers to the fact that in physical proximity, a lot of issues concerning trust and security are tacitly taken care of .

Why do I blog this? I guess it's a smart summary of proximity-based services, dealing with various dimensions (like safety or belongings).