An automated method that generates crowd-sourced event notifications includes: retrieving sensor data from mobile devices; detecting events based on the retrieved sensor data; and generating a set of summary nodes based on the events, where each summary node is associated with multiple events. A system that generates crowd-sourced event notifications includes: multiple mobile devices, each having at least one sensor, each mobile device identifies events using calculations based on sensor data and generates a notification for each identified event; and an analytics server that generates a set of summary nodes based on the identified events, each summary node associated with multiple events. An automated method that generates event notifications includes: retrieving sensor data; calculating a set of statistical values based on the sensor data; comparing the statistical values to at least one threshold; and generating an event notification when the threshold is exceeded by any of the statistical values.