Ringen is an iBeacon enhanced Android and iOS app for meeting up with people at "Ringen" in the Stockholm C Train Station main hall. Users input a "slogan" string shared in beforehand among the people wo are going to meet and the app detect the proximity to an iBeacon device installed at "Ringen" aka "Spottkoppen" in the Stockholm City Central Train Station main hall. The proximity to the beacon for each app/phone is reported to a central server and this info gets radiated out to all the apps that use the same slogan. That way app users can become alerted that other attendees are in the vicinity of the meeting spot and can send BUZZER SIGNALS (!) or text/voice messages to these people as a way to NUDGE them, telling "I am here too" or "soon there, my train is late". Ringen - where Kind of Stupid becomes Plain Fun ?
The project will produce the Android app first, followed by the iOS version.
UPDATE: As per February 2021 Ringen has so far not been implemented. But not too late. It is possible that the 'ringen' opening in the Station hall is still there. If not you can simply fork this thing, rename the app and simply pay tribute to some other meeting location. The principle remains the same. You are supposed to meet up with other iBeacon users and when those people come in proximity you become notified. A likely evolution is that each person to meet up carry their own iBeacon. Some think iBeacons are dead but it's not true. You could be the person renewing the interest.