Q: In the Find My Friends app, once you power your phone off, with for example a little more than 20% charge left, what location shows to your followers? I always thought it would say “Location Not Found,” but a friend told me it will just register as your last location before you powered down. Which is it?
A: The correct answer is actually somewhere in the middle, and a bit different from what you might expect.
Unlike other services such as the recently retired Google Latitude, Find My Friends doesn’t actually track your location and report it to Apple’s servers automatically in the background. Instead, it runs passively on your device, waiting for your friends to request your location. When one of your friends starts up the Find My Friends app, it sends out a request from their device to your iPhone, which in turn fires up your GPS, figures out where you are, and reports that location back to their device.
This means that if your device is off, your friends should normally see “Location Not Available” since your device is unable to respond to a request to report its location.
There is one additional catch here, however: the Find My Friends app on the receiving end will remember and display a user’s last reported location for up to two hours. This means that once your iPhone is shut off—or even if you’ve simply moved out of data coverage by going into a building or subway—your friends will still see your location from any time they requested it within the past two hours, time-stamped accordingly. Note that this is not necessarily the location that you left coverage at, but where you were the last time they checked. Once it’s been more than two hours since the last location update, the app will simply go back to showing “Location Not Available.”
To summarize, if your iPhone is off or out of coverage any friends who have requested and received a location update from you in the past two hours will still see you at that location. Those who do not have a location report from you in the past two hours will simply see “Location Not Available.”
This “passive mode” approach actually saves battery life in most cases as GPS-based location services consume more power. Since location services aren’t being used by Find My Friends except when somebody wants to know where you are, most of the time your device isn’t reporting its location. Of course, if you have several dozen friends requesting your location very frequently, you may see the opposite effect on battery life, but one could argue that’s a social issue rather than a technological one.