There has been talk for sometime of using mobile phones, Wi-Fi and GPS technology for interpretation and marketing. The new iPhone has a WhosHere function and it could be used for marketing or interpretation. You could send messages or call any mobile phone user passing by – but the technology is highly intrusive.

Mathew Honan has written a very disturbing piece in Wired Magazine I Am Here: One Man's Experiment with the Location-Aware Lifestyle

“The location-aware future—good, bad, and sleazy—is here. Thanks to the iPhone 3G and, to a lesser extent, Google's Android phone, millions of people are now walking around with a gizmo in their pocket that not only knows where they are but also plugs into the Internet to share that info, merge it with online databases, and find out what—and who—is in the immediate vicinity. That old saw about how someday you'll walk past a Starbucks and your phone will receive a digital coupon for half off on a Frappuccino? Yeah, that can happen now.
Simply put, location changes everything. This one input—our coordinates—has the potential to change all the outputs. Where we shop, who we talk to, what we read, what we search for, where we go—they all change once we merge location and the Web.”
Think more than twice about this technology – read his piece at
http://www.wired.com/gadgets/wireless/magazine/17-02/lp_guineapig