When we speak about Location-promoted visits, we are talking about visits attributed to a marketing campaign: Attributed visits.

There are several options to measure these:

Beacons: by placing beacons in a store you can track the mac address of a user’s phone (if the beacon uses WiFi) or directly the IDFA (if they use Bluetooth + an SDK).
SDKs: by placing software (SDK) within applications that have a considerable market share, such SDKs can be the trigger that identifies a user going within a geofence. Of course, any users that have disabled lat:long communication in the background for such apps, or any that do not have such apps, cannot be counted as visits. This is the methodology used by Adsquare.
Bidstream: by analyzing incoming bid requests in a programmatic ecosystem you can find users within a geofence. Of course, any users that are not active with apps connected to the right SSPs and sending traffic to the party measuring at the time they went into the store will not be counted as visits. This is the methodology used by mediasmart.