How many times did you call your wife in a mall to find where she ended up (or vice versa)? It happens to all the time.
Now there is these system by Navizon that is exploiting WiFi localization on the assumption that people leave the WiFi on, on their smart phone.
Take a look at system in action:
To work it requires a number of WiFi antennas spread around the place, and this is reasonable assumption in a large space like a mall. By triangulation it can achieve a remarkable precision on where a smart phone is (and the purse holding it). The app uses this information to guide you to interception, with a user interface that really reminds of the radar.
This apps just show the many things that can be done with a smartphone. May be you might wish this app not to be on your wife smart phone if you are trying to hide yourself in the vastness of the mall, but those are the downturns of technology.
Beyond jockeying, it is clear that privacy issues go hand in hand with localization services and in this case there is now opt out solution. Either you switch it off (at least the WiFi part) or you can be tracked.