I Guess There is an App for That
According to this article, an app for the new iPhone 4s has enable a husband to ascertain the location of his wife through her iPhone. The app at issue is called “Find my Friends” and it lets people find out where people they know are through the location of their iPhones. Of course, there are probably security settings that turn off “Find my Friends”. I would suspect that, had the wife known that her husband had innocently installed the app on her new iPhone, she probably would have turned off “Find My Friends”.
People should be conscious of programs that indicate where they are (Find My Friends, FourSquare, “Check In” on Facebook, etc.) If you really do not want people to know where you are, then you should make sure these programs are closed.