The Apple Watch was supposed to become the new thriving platform and App Store for third-party apps. 10 months later, it's hard to name popular Watch apps. And there are reasons why the Apple Watch App Store isn't as vibrant as the iOS App Store. But some developers, such as David Smith, have found ways to make your Watch more useful.

Sleep++ isn't a new Watch app. But today's major update adds many important features making it a useful free app for anyone who wants to track their sleep. Sleep++ turns your Watch into a sleep-tracking device and gives you insights about your sleep. As long as you keep your Watch in airplane mode and charge it when you take a shower, you can keep it on your wrist 24/7.

Sleep++ leverages the accelerometer in your Watch to register deep sleep, light sleep, restlessness and wakefulness. I've been using it for the past week and it's interesting to wake up in the morning and get instant feedback about your night. It's been pretty accurate in my experience.

Using it isn't too cumbersome as the Watch app only has one button — a start/stop button. Today's update improves the sleep analysis, lets you synchronize your sleep data with the Health app and other HealthKit apps and adds the ability to trim your night if you forgot to turn Sleep++ off when you woke up.

David Smith reports on his blog that the app has been downloaded 170,000 times. It seems like an incredible number given that only a few million people have bought an Apple Watch over the past few months. But fitness is one of the core features of the Apple Watch and Apple doesn't provide a default sleep tracking feature.

Sleep++ proves that there's room for Apple Watch apps. There aren't as many Apple Watches in circulation as there are iPhones or iPads. Developers are still figuring out how to take advantage of the Apple Watch. It's unclear if third-party apps even make sense on a Watch in the first place. And the first version of the Apple Watch feels underpowered.

And yet, 170,000 downloads is quite impressive and should make third-party developers hopeful. Down the road, with a more powerful Apple Watch, more APIs and a bigger install base, there might be a future for Apple Watch apps.