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. This includes the Compass and the new Noise app. However, the weather, battery level, and time can be seen even when the screen is dimmed. The Apple Watch Series 5 still did a pretty good job of tracking our workouts, including some high-intensity interval training and running. Its heart rate sensor is very accurate and quite quick too.