If you want to automatically send out a notification to users of your app when they enter a particular geographical area then consider purchasing one of more Geofences.
The Geofence works on the basis that your customers smart phone is with them and the GPS on the smart phone is continually updating its own position. You can take advantage of this fact and proactively alert your customers to a particular offer if they travel into an area that you define.
A Geofence is required for each geographical area. We work with you on defining the rules for activation (e.g. when a user is in a particular geography for longer than 15 minutes on business days) and we allow a notification update each month for each Geofence in operation.