GPS model lets you take calls and reply to texts from your wrist Large Retina OLED display Up to 2x faster processor than Series 3 Track your daily activity on Apple Watch and see your trends in the Fitness app on iPhone Measure workouts like running, walking, cycling, yoga, swimming, and dance Swimproof design High and low heart rate notifications and irregular heart rhythm notification Sync your favorite music, podcasts, and audiobooks Pay instantly and securely fr