With all the prior art in the area of location based alerting (stalking) Apple can't think they'll actually defend any of the claims that might get allowed.
In 2004, Bounds, etal, from Texas A&M wrote...
"When two or more ReConnect devices come into range of one another, their desired interaction levels as well as personal data and location is exchanged via a Bluetooth ad hoc network."
Then there is Weilenmann & Holmquist in 1999 with their Hummingbird...
"...we developed the concept of inter-personal awareness devices, IPADs... The Hummingbird is an IPAD which enhances the awareness of presence between the people in a group by extending their range.
"A notion that came up in the focus group session was that the Hummingbird could be seen as a means to achieve status; users appeared more important when carrying technological equipment."
And, of course, who could forget the LoveBomb...
"When a button is pressed, an anonymous message will be sent to people (LoveBomb owners) who are positioned within a certain radius from the initiator of the message. The LoveBomb uses tactile cues - the heart message makes the device vibrate in a manner that resembles pulsating heartbeats, while the message of sorrow is characterized by irregular vibrations."
ReConnect: A Mobile Tool for Enabling Social Interaction (2004)http://www.cens.ucla.edu/pub/CS219-Spring06/Anonymity%20Reading%205.08.06/Bounds.pdf
Hummingbirds Go Skiing: Using Wearable Computers to Support Social Interaction (1999)http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.65.1920&rep=rep1&type=pdf
The LoveBomb: Encouraging the Communication of Emotions in Public Spaces (1999)http://www.viktoria.se/~tobias/pub/lovebomb.pdf