Very happy with the Mi Band 3 - battery lasts about 10 days with continuous notifications and HR. Notifications work about 95% of the time and the band supports any app's notifs.
Heart rate is a little questionable but is generally accurate when worn properly. Sleep tracking is great.
Model: Mi Band 3
Wireless connection: Bluetooth 4.2 BLE version
Battery Capacity: 110mAh/Lithium polyme
Standby time: 20 days
Input voltage: DC 5.0V
Input Current: 250mA Max
Waterproof Rating: 5ATM(50 meters)
Phone requirements: Bluetooth 4.0 ; Android 4.4 or iOS 9.0 or above.
Sensor: 3-Axis Accelerometers, PPG Heart Rate Sensors
Screen: 0.78 inch /OLED display/Touch screen
Display resolution: 128 x 80
Working temperature: -10°C～50°C
App: Mi Fit
Size: 17.9 x 46.9 x 12mm
Total length: 247 mm
Adjustable Length: 155-216 mm
Fitness Tracker, Heart rate monitor, Pedometer, Smart reminder(Message, Call, App notifications), Sleep monitor, sedentary reminder, Vibration alarm clock, Sports data...
Automatic Unlocking: supports models based on Android 4.4 or higher MIUI system, or Android 5.0 or above, and supports Smart Lock model
manual is chinese but app support most international language like english, german, spanish, etc
1 x Mi band 3(International version)
1 x USB Charging Cable