I am a Xiaomi convert. This is a smart watch that looks smart, and is comfortable. I am happy to sleep with it on, and keeps track of sleep patterns. Pedometer is accurate and functionality is user friendly.
The battery life is exceptional.

Mi band 4 is not much different from mi band 2 which I have used for more than 2 year and still going strong, especially the battery.
Mi band 4 is pretty much the same although it is more fun as you can choose photos and it has colours (unlike other mono colour mi bands). Mi app that comes with the band is not the best nor the most accurate. But even the more expensive trackers are not accurate. I guess if this can last for more than 2 years it does a great job.

Picked up this fitness watch off Amazon for $55. This fitness tracker is pretty cool. It has a nice bright colour screen and long battery life. It comes with a charger. It has text and call notifications and weather forecast just to name a few. Works with most android phones and iOS 9 and above. I use it with iOS and I love it. Its very responsive. See video review here:
https://youtu.be/Y0J3e6zDTkk

I really love my Xiaomi Mi Band. Its battery last a lot. You can swimming with it. It really fit in your wrist, feels so good. Looks elegant and sporty with your outfit.

Wore 1 day and it burned my wrist 1cm / 1/2 cm almost healed 4 days later. It is caused by the pulse detection LED's that get very hot if using many pulse readouts. Apparently this happens with many Smart Watches. Emailed the manufacturer to see if I could get a User Manual they told me to go to the eBay seller...?? very disappointed with that reply.