2018–2025[]
ECG was introduced with watchOS 5.1.2. It was compatible only with the Apple Watch Series 4 and only in the US and US territories.
2025–present[]
| Applications and services Activity | Alarms | Apple Developer | Audiobooks | Blood Oxygen | Calculator | Calendar | Camera Remote | Clock | Compass | Contacts | Cycle Tracking | Depth | ECG | Find Devices | Find Items | Find People | Heart Rate | Home | Mail | Maps | Medications | Memoji | Messages | Mindfulness | Music | Music Recognition | News | Notes | Noise | Now Playing | Phone | Photos | Podcasts | Reminders | Remote | Settings | Shortcuts | Siren | Siri | Sleep | Stocks | Stopwatch | Tides | Timers | Tips | Translate | Vitals | Voice Memos | Walkie-Talkie | Wallet | Weather | Workout | World Clock Discontinued  |