watchOS 5.2.1 can be downloaded for free through the dedicated Apple Watch app on the iPhone by going to General -> Software Update. To install the new software, the Apple Watch needs to have at least 50 percent battery, it needs to be placed on a charger, and it needs to be in range of the iPhone.
The watchOS 5.2.1 update is minor in scale and focuses on performance improvements and bug fixes discovered since the release of watchOS 5.2. There were no changes discovered during the watchOS 5.2.1 beta testing period, and according to Apple's release notes, the update makes the ECG app and irregular heart rhythm notifications available in Croatia, Czech Republic, Iceland, Poland, and Slovakia.
This update includes new features, improvements and bug fixes:Work on watchOS 5 is set to wind down over the course of the next month as Apple transitions to watchOS 6, which is expected to be unveiled at the Worldwide Developers Conference in June.
- ECG app on Apple Watch Series 4 now available in Croatia, Czech Republic, Iceland, Poland and Slovakia
- Irregular heart rhythm notifications now available in Croatia, Czech Republic, Iceland, Poland and Slovakia
- Fixes an issue where the numbers on the Explorer face would not appear for some users