Abstract: A system for sensing, analyzing and reporting a collision event experienced by a person or object sensor module designed to a person or object, module angular velocities over time and a processor for analyzing the sensed velocities, calculating properties of angular velocities, such as jerk and jolt, comparing these properties with threshold values selected to correlate to predicted severities of injury to the person or object, transmitting information regarding these properties to communication device user-designated persons. Also provided are group tracking and communication devices for use by monitors to manage multiple persons equipped with sensor modules. The sensor modules and group tracking and communication devices are designed to be portable, attachable and detachable so that they can be attached to different types of gear used by persons engaging in different activities.