Compatible OS Android 5.1 or above; iOS 10.0 or above, Brand KOSPET, Operating Mode Full-Touch, Product Name TANK M1, APP Name Da Fit, Bluetooth Version BT 5.0.
Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
1. ($55.24): BG284c49
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): TANKM1FANS, BGd086ee, BGJP99333, BGb227a5, BG8ede1d, BGb9bac2, BG6ad230, BG87a8a2, BG95b8a8, BG8f0384, BG14b8f3, BG4faf7a, BG6b13a6, BGJP116, BGbf11dd
(there’s a little possibility that old coupon will work)
Price history and price alert
Do you need price history chart (for all/most countries) for KOSPET TANK M1 Smart Watch? There we go. The lowest price was: $39.99.
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)).