When the Apple Watch Series 4 was announced last week, three new heart monitoring features were discussed: Low heart rate monitoring, detection of AFib, and the new ECG feature. At the time, Apple gave the impression that these features would be on the Series 4 only but, as it turns out, at least one of them is available for previous series too.
If you open up the Heart app on your Apple Watch, you will now see the option to enable and detect low heart rate. I can confirm that it is available on the Series 3 (see the screenshot after the break) and a friend confirmed that on her Series 2 she has the option. That means, at least when it comes to this new heart monitoring feature, it is a WatchOS 5 feature, not device specific.
You can configure the low heart rate monitoring to give you an warning if your heart rate is lower than 40, 45, or 50 beats per minute over the course of 10 minutes. This can be vital information for your doctor and your overall health.
This ability to monitor a low heart rate joins the previous high heart rate monitoring feature that has been a part of the Heart app on Apple Watch. That feature works essentially the exact opposite way as the low heart rate monitoring, giving you a notification if your heart rate is above 120 beats per minute with no detected activity for 10 minutes.
Kudos to Apple for making this available to everyone and not requiring you to purchase the new Series 4 to get it.