With the SPOT Gen3 GPS Messenger Personal Tracker, help is only the push of a button away. SOS button alerts GEOS International Response Coordination Center of emergency situations and initiates your rescue. Help-assist button allows you to ask for help from your friends and family and send them your location. Check-in button lets your contacts know where you are and that you are OK. Track button allows your contacts to track your progress using Google Maps. Custom-message button sends a pre-programmed message with your GPS location. GPS uses satellites to communicate where cell phones can't. Custom track rates refresh your location every 2, 5, 10, 30 or 60 minutes. Vibration sensor tells Spot to send your location when you start and stop moving. With the enhanced tracking plan you can track your progress continuously. Rated to handle fog and humidity. Operates in temperatures from -22°F to 140°F and at altitudes ranging from -328 ft. to 21,325 ft. Designed to provide an extended battery life. Includes batteries, USB cable, carabiner, quick reference guide and carrying strap. Dimensions: 3.4"L x 2.6"W x 1"W. Weight: 4 oz.