The location service that allows applications to know when a user has crossed a specific location to trigger an automated action is; Geofencing
Geofencing is a location-based service whereby an app or software uses GPS, RFID, Wi-Fi or even cellular data to trigger an already programmed action when a mobile device enters or exits a virtual boundary that is set up around a geographical location called a geofence.
Thus, the answer to the question would be geofencing as it tallies with the definition given above,
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