The sensor has a small 1x2 inch screen. Once the collar is on your dog (see How to Install) your dog's health status wiil appear on your screen. Your screen will have a specific code to it and when you download the app "The Healthy Dog" it will ask for a code. Once you type the code in it will link your phone to the collar. It will also show the health status on your phone. This collar also has GPS tracking. If your dog is sick it can find out where and how he/she gets sick. If the collar thinks your dog is sick it sends you a notification whether your phone is on vibrate or not. When you get a message and your dog is sick it will tell you what type of sickness your dog has. You also get daily health reports on how your dog is doing.