Your iPhone logs where you are and when you're there
You were outraged that the NSA was tracking you—but, did you know that your iPhone keeps a map of where you've been and a log of how long you were there? It's on by default and buried deep within your preferences.
Don't believe me? Go to
Preferences > Privacy > Location Services > System Services > Frequent Locations > History.
This data has a tremendous amount of noble uses. Check out the app called Moves. It operates in the background and keeps track of your movement through out the day—it's like having a Fitbit or Nike Fuel Band without having to buy anything extra. I'd also love to see an app made that categorizes where I'm at throughout the month to help me be audit how I'm spending my time and offer suggestions.
This data could also have many ignoble purposes—if this creeps you out feel free to pass on the public service announcement and let people know they can turn this off.