I’m not sure if i should add this here or in a new post, but i also feel the need to use some of the functionality requested here, in particular the access to the geofencing api.
The main goal is to use the device location services in a practical and battery-efficient way.
Here are some scenarios that i can think of:
an airline app can define a geofence around an airport when a flight reservation is near boarding time. When the device crosses the geofence, the app can send a notification that takes users to an activity that allows them to get their boarding pass. (taken from google geofencing api)
Travel guide assistance - Could define multiple interesting areas around a city, accordingly to the user interests, and warn users when they are entering or leaving that area of interest.
There exists such functionality in native apps, for example in andoid and in ios.