Communication between users of mobile devices is provided based on proximities between the users. Users are given unique identifiers, which are stored on a server, and mobile devices with the unique identifiers broadcast transmissions with their unique identifiers. The mobile devices listen for incoming identifiers from other mobile devices, and devices are detected directly or through an externalradio communication device or hotspot. Additionally, indirect detection through another mobile device or hotspot is used to linking the first mobile device and the second mobile device. The detectionis used to form a group of two or more mobile devices, providing at least a subset of profile information associated with the list of users in the group to the first mobile device to form proximity groups.