Techniques and systems are disclosed for enhancing the flexibility and resiliency of mobile social networking platforms. Techniques enable dynamic, user-defined check-in points with mobile devices so that users may define ad hoc, location-based communities. Techniques may also selectively determine an appropriate location-sensing mechanism to improve location accuracy or privacy, or to compensate for unavailable location-sensing capabilities. The techniques may assist social networking platforms to have a greater range of check-in options and to enable communication that may not rely on traditional network connectivity. In some cases, devices belonging to participators outside the member group may be used to locate a member who has moved outside the detection zone of a check-in point. In some cases, the participators' devices might not be directly connected to the lost member device but instead are connected via one or more “hops” of indirect communication with other participator devices.