Earlier this week, "Underscore" David Smith released a new app for Apple Watch called Sleep++. If you've ever used a sleep tracker app like Sleep Cycle for iPhone, you'll understand this one pretty quickly. It uses the motion-tracking capabilities of your Apple Watch — courtesy of improvements in watchOS 2 — to monitor how well you're sleeping at night, in terms of quality and duration.

It's easy to use:

1. Wear your Apple Watch at night.
2. Tell the app when you're laying down for sleep.
3. In the morning, tell it when you wake up.

It optionally syncs with Healthkit too, so you can easily and privately sync your sleep data with other health apps.

In a blog post published the day he released Sleep++, David allayed concerns about wearing Apple Watch at night rather than charging it:

To use the app you need to wear your Apple Watch while you sleep each night. This presents an obvious problem, when do I charge it? [...]

The TL/DR is to charge your Apple Watch in the morning while you get ready for your day (take a shower, get dressed, etc) and then again in the evening while you get ready for bed (brush teeth, put on pajamas, etc). Then put your Apple Watch in Airplane Mode while you sleep.

He also brought up a neat point I hadn't thought of:

Another side benefit of wearing your Apple Watch all night is that you can easily set completely silent alarms to wake you up. I really like being able to be awoken by a gentle tapping on my wrist and get out of bed without disturbing my wife. Just make sure you mute the chimes before you head to bed.

Sleep++ is free to download, with a mere $2 in-app purchase to remove advertisements and support the app's development. (I think he should just charge $5 for the app upfront, but that's just, like, my opinion, man.)