Apple’s Find My Friends app, released in 2011 for the iPhone and iPad, works with Siri to give you precise directions to the location of your other Apple product-wielding friends. Users choose to share their locations for a few hours or indefinitely. Ask Siri “Where’s (friend’s name)?” and the app’s map shows where they are in relation to you, as well as an approximate address for play-by-play directions.
Only friends who have accepted your request to see their location can see where you are, or allow you to see where they are. Users are signed out of the app after 15 minutes of inactivity and Apple’s servers only keep last-known-location data for two hours, according to Apple's website.