Google Maps. The user can control the accuracy and details of what each of the other users can see. The precise location can be turned on, or be limited to the city identification. The privacy can be turned off by the user, or a location can be manually entered instead.
On July 10th, 2013, Google announced plans to shut down Latitude on August 10th, 2013. This is what they said, also located here.
Checking in to your favorite places is a great way to let people know when you're somewhere important, but there are plenty of in-between times when you might want close acquaintances to know where you are so they can tell when you got stuck in traffic or got home safely. That's when Latitude comes in -- or, perhaps we should say, came in. As part of its Maps redesign, Google is sending its Latitude service the way of Google Reader. Latitude gets lost on August 9th, less than a month from now, and all of its various location-centric APIs will wander offline at the same time. Additionally, Google is removing check-in functionality from Maps, asking that you use Google+ instead, which is also where you'll have to turn if you want to share your location with friends -- a feature not currently enabled in the iOS version of the app. Google promises that functionality is "coming soon," so in the interim please tell your significant other the same when they ask what time you'll getting home from work.