Apple Watch Series 4 (GPS) 40mm Silver With White Sport Band(642)

Generate an ECG Anytime, Anywhere

The built-in titanium electrode in the digital crown and the sapphire crystal electronic heart sensor on the back of the Apple Watch gives you the ability to record your own ECG, or electrocardiogram. It's similar to a single-lead electrocardiogram and takes only 30 seconds to create. Just touch the digital crown and wait for the Apple Watch to generate your ECG waveform. 
The ECG app is meant to help you detect whether you're heart's beating at a normal sinus rhythm, or if your rhythm shows signs of irregularity, or atrial fibrillation. Your ECGs are stored in the Health app on your iPhone and you can share them with your doctor.

Heart Rate Sensor

Apple Watch Series 4 regularly monitors your heart throughout the day, so you can check your heart rate anytime and keep track of your heart’s performance. What’s more, if it detects unusually high or low heart rates, it alerts you — even when you don’t feel symptoms.

Fall detection

With the new accelerometer and gyroscope, Apple Watch Series 4 can detect that you’ve fallen. When an incident like this occurs, a hard fall alert is delivered, and you can easily initiate a call to emergency services or dismiss the alert. If you’re unresponsive after 60 seconds, the emergency call will be placed automatically and a message with your location will be sent to your emergency contacts.

Emergency SOS

Emergency SOS allows you to quickly get help. It calls emergency services, notifies your emergency contacts, sends your current location and displays your Medical ID badge on the screen for emergency personnel. And Apple Watch Series 4 with mobile connectivity does it all even when you’re away from your phone.

Activity Rings

Three activity rings on the Apple Watch Series 4 are designed to help you measure all of the ways you move throughout the day. As you move, each ring begins to close, giving you additional motivation to close your rings and increase mobility.
Move: The Move ring tracks the active calories you burn. Active calories are the ones you burn through all kinds of movement, from taking the stairs at work to playing with the kids.
Exercise: The Exercise ring shows you how many minutes of brisk activity you've done, whether you're working out or just moving at a fast pace.
Stand: Sitting too much has the potential to contribute to health problems over time. This ring is designed to keep track of the amount of times you stand throughout the day.

Apple Pay

Charge purchases to your credit or debit card simply by activating Apple Pay and holding your watch to a compatible checkout reader. You can also send or receive Apple Pay Cash via the Messages app. No matter how you use it, Apple Pay is designed to keep your financial information completely private and secure.