Up to now, the lack of sleep tracking was one of the biggest omissions from the Apple Watch’s initial feature set when it comes to fitness and daily activity tracking. Sleep is an integral part of health and fitness, and practically all other competing fitness trackers have been able to track sleep for years.

The Apple Watch actually does have all the necessary sensors to track sleep, but it was designed with the assumption that you’ll charge it overnight, which means you won’t be able to wear it at night in order to track your sleep. Or so we thought.

Enter Sleep++, the new Apple Watch app by Mr. Underscore, David Smith. Sleep++ promises to track your sleep and still leave you with enough battery life to use your Apple Watch normally throughout the day. From Mike Bates’s initial impressions:

This is all well and good, but the main concern I had with such an idea was the battery life of the watch and if I’d still be able last all day if I wasn’t charging overnight. From my extremely brief testing (cough - only one night so far cough) it seems as if David’s proposed solution - charging the watch when you’re getting ready for bed and then again when you’re getting ready in the morning - might actually work out as he’s indicated.

Apparently, it does:

Having said that, last night I was able to charge my watch up to 86% before bed, track my sleep in airplane mode overnight, wake up with 80% still left, and then charge the watch fully up to 100% while I got ready this morning. I tracked my sleep data, it got fed into HealthKit, and I got to wake up with my watch tapping my wrist as opposed to a blaring alarm. Not bad.

This is very, very interesting. It’s still mostly a workaround or, if you will, a hack, but it does allow you to use a feature that until now remained inaccessible.

The fact that this workaround is at all possible is a testament to how quickly the Apple Watch’s battery can be recharged. The only asterisk I can think of is whether it will have a negative impact on the battery’s useful life in the long run.

The fact that the Apple Watch, as many other consumer electronic devices, indicates a 100% charge after a few minutes doesn’t mean it’s really fully charged. There are some benefits to leaving devices to charge overnight, so that they continue to be plugged in for a few hours after their battery indicators hit 100%.

I guess if there are some negative side effects to doing this, once apps like Sleep++ become popular, we’ll start hearing about them soon enough.