Just check coupons out (with price alert and history). Do you want to know what the best price is?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Standby Time: About 40 days, Resolution: 240*240pixels, APP Name DaFit, Charging Time: About 2.5 hours, Type: TFT, Battery Capacity: 280mAh, Charging Type: Magnetic Charging, Size: 1.3inch, Bluetooth Version BT 5.0, Personalized Watch Face Support, Blood Oxygen Monitor Support, Waterproof 5ATM Waterproof, Using time: About 15 days
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
1. ($17.99): BG8a509b
2. ($40.24): BGc70579
apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): band10, BGWRIBAND10, BGb58412, BG51f436
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for UMIDIGI Uwatch 3S Fitness Tracker.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).