Health Features 

Apple Watch Ultra 3 includes a third-generation optical heart rate sensor that calculates metrics like calorie burn, resting heart rate, and a heart rate that's too high, and the electrical heart rate sensor can be used for taking electrocardiograms, while LEDs and infrared light enable blood oxygen monitoring. A built-in accelerometer and gyroscope enable other important health-related features such as fall detection.

The Apple Watch can detect a low heart rate, a high heart rate, and an abnormal heart rate, monitoring for health problems like atrial fibrillation and sending notifications when anomalies are detected.

Hypertension Alerts

The heart rate sensor in the Apple Watch Ultra 3 powers a new feature for detecting high blood pressure. The Apple Watch isn't able to measure specific systolic and diastolic pressures, but it looks for signs of hypertension in heart rate data.

ECG 

The ECG app uses sensors on the bottom of the Apple Watch and the Digital Crown to take a one-lead electrocardiogram. It detects heartbeat and rhythm, and can let users know if atrial fibrillation is detected or if the heart is in a normal sinus rhythm.

Durability 

Because it is meant to be used for exploring and adventuring, the Apple Watch Ultra is able to withstand more extreme temperatures than standard Apple Watch models. It works in temperatures as cold as –4° F (–20° C) to to as warm as 131° F (55° C).It is certified to MIL-STD-810H, a standard that is used for military equipment and employed by rugged equipment manufacturers. Apple says this testing includes Low Pressure (Altitude), High Temperature, Low Temperature, Temperature Shock, Contamination by Fluids, Rain, Humidity, Immersion, Sand and Dust, Freeze/Thaw, Ice/Freezing Rain, Shock, Vibration, and more.