The following are the scenarios that the Geolocation external object is designed to solve.
Where are all the Facilities of my company?
Which gas station are within a mile from me?
The canonical case would be to create an app which will show the Top 5 Customers near my current position.
How To: Geolocation - Show points near me
Which is the location of this accident?
Which is the location of this restaurant?
The canonical case of use would be to develop an app that enables the user to report transit issues and one key piece of information can be the location of that issue.
How To: Geolocation - Showing My Location
How did the truck got to that place?
Where is the route this cab did?
A canonical case of use would be tracking vendors in mobile point of sale applications.
To use this API in iOS is important to set the Location when in Use Usage Property
How To: HowTo: Use Location Tracking