Guudgo Tuya WiFi Human Body Sensor (Banggood, Aliexpress: Battery: AAA battery * 3 (not included), Operating humidity: 20%-85%, Color box size: 85x 85x 38MM, Working temperature: 0-40 degrees (32F-104F), Standby time: 1 year, Protocol: IEEE 802.11b/g/n, Product size: 63x 63x 22MM, Weight: 70g, Wireless range: 45m, Storage temperature: 0-90%, Wireless type: 2.4GHz (the best price with coupon)).
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 coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
1. ($18.23): BG589b2e
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Old coupons (from the oldest to the newest): BG611daf, BG00c906
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for Guudgo Tuya WiFi Human Body Sensor. The lowest price was: $7.79.
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)).