Apple didn't make a sleep tracking app for the Apple Watch for years and years. Its rationale was that the Apple Watch's battery life, which typically lasts about than 24 hours, wasn't prepared for it, and Apple therefore recommended that you charge your Apple Watch at night instead. This didn't stop people from wanting a sleep tracking app for their Apple Watch — and several third-party developers obliged.
Of course, Apple officially released its own sleep tracking app — Sleep — as part of watchOS 7 (in late 2020), and it's compatible with every current Apple Watch (Series 3 or later). Apple's new Sleep app works very similarly to the third-party sleep apps that you may or may not have used for years. And yes, it integrates your sleep tracking data directly into Apple's Health app.
But there are still reasons to use a sleep-tracking app that's not the Sleep app. It mostly comes down to user-interphase and the way you view the data that the app actually tracks. Because, well, Apple's Sleep is pretty basic (which some people might like, and others will desire something more).
What Sensors Are Used for Sleep Tracking?
The Apple Watch primarily uses two sensors for sleep tracking: its accelerometer and its heart rate sensor. The accelerator is used to track your body's movement throughout the night, whether you are tossing and turning or being still; it's also used to track your respiratory patterns or how many times you take a breath per minute during your sleep. The heart rate sensor is used to measure your heart rate and then compare it with your breathing patterns. The Apple Watch will analyze your metrics to determine how deeply or lightly you were sleeping at a given part of the night.
Key Features to Look for
Automatic sleep detection: This is a pretty obvious yet really important feature for any sleep tracking app. Instead of making you initiate when you fall asleep, the app uses the Apple Watch's sensors — such as heart rate, accelerometer (for breathing and movement) and mics (for noise) — to identify when you fall asleep. The end result is a more convenient and more accurate way of tracking sleep.
Sleep quality: Most sleep tracking apps for the Apple Watch show you stats about your sleep and also how well (or deep) you were sleeping during the night. In the morning, you can then check your stats to see when you were sleeping well (or deeply) versus no so well (or lightly)
Sleep schedules and goals: Most apps allow you to set sleep schedule goals. You can have different schedules for different nights of the week, of which you'll get alerts when it's time to start winding down (stop looking at screens) and getting your body ready for bed. You can also set wake-up times, too.
The Best Sleep-Tracking Apps
Apple's Sleep app is certainly the most convenient sleep-tracking app because it's native; so long as your Apple Watch is running watchOS 7 (or later), the app is just there. It integrates seamlessly with your iPhone's Health app. One unique feature is that the Sleep app will let you know if your Apple Watch's battery is below 30 percent when it is getting closer to your normal bedtime; this way you'll be able to charge the smartwatch before you go to bed. According to Apple, an hour-and-a-half charge will take any of the Apple Watch from about zero to 80 percent battery; while an extra half-an-hour is needed to charge that extra 20 percent. Aside from this, the Sleep app is fairly basic in the data it can actually tell you, which basically boils down to total sleep time and your various heart rates throughout the night.
This was the most popular Apple Watch app for sleep tracking before Apple officially launched its own. It looks and works very similarly to the Fitness app — there are rings and everything. It tracks sleep duration, sleep quality and “readiness,” the latter basically attempting to rate how well your sleep prepared you for the forthcoming day. And it integrates nicely with Apple Health.
Sleep++ is another sleep-tracking app for the Apple Watch that has developed a loyal user base. One of its biggest upsides is that it’s free. It also has some other neat features, such as automatic sleep tracking (it detects exactly when you fall asleep) and it can tell you how many times (and for how long) throughout the night you're in a deep sleep. Additionally, it allows you to set sleep schedules and goals, similar to other sleep-tracking apps.
Pillow is a well-reviewed app that, again, has many of the popular features like automatic sleep tracking and in-depth sleep analysis charts. It has a “smart alarm clock,” which wakes you up at the optimal point in your sleep cycle for maximum morning refreshment. The app can also record audio (like snores and random outbursts) during the night and play it back for you, but that requires you to pay a subscription fee so you’ll have to want it really bad.