Apple Watch Series 5 has built-in GPS and is swimproof. Built-in cellular lets you receive calls, send texts, and check your email — even without your phone. With the ECG app, you can take an ECG similar to a single-lead electrocardiogram right from your wrist. The optical heart sensor can monitor your heart rate and alert you to a high or low heart rate. You can store your favorite music, podcasts, and audiobooks on your watch. A built-in compass and GPS enable precise navigation through Maps, while the altimeter tells you how high you go — great for outdoor workouts.