This model from Withings has many useful features. This model comes with an OLED (AMOLED) screen.
From Amazon
Withings ScanWatch – Hybrid Smart Watch with ECG, Heart Rate, Oximeter - 30 Day Battery Life - Smart Watches for Women, Smart Watch for Men, Fitness Tracker - Android & iOS
OnBuy
Hybrid Smart Wristband 42mm with ECG and SpO2 Scanwatch Withings white - White