For outdoor locationing, we also utilize the most popular locationing technology—GPS. To ease adding a personalmeaningful location into the database, we use Google Maps as the user interface in our application. That is, by clicking at a specific location on the Google Maps, users can add that location into the database and then use it in locationbased reminders. As noted in Sect. 3.2, in the location database, indoor locations are associated with the discovered MAC addresses of the Wi-Fi APs, so the indoor locations should be pre-visited by the users. However, outdoor locations are treated differently—we associate outdoor locations with their GPS coordinates. Most importantly, since the GPS coordinates of the outdoor personal-meaningful locations can be obtained from the Google Maps API, the users are not required to be physically located at those locations before using them in the reminders.