$11.99 – Tuya WiFi Smart Carbon Monoxide Detector (Banggood, Aliexpress: Tuya WiFi Smart Carbon Monoxide Detector Alarm 85dB Sound Warning LCD Digital Display Home Indoor CO Poisoning Siren (the best price with coupon)).
You can get Tuya WiFi Smart Carbon Monoxide Detector for $11.99 with coupon (from Banggood). You can create price alert here, copy coupons and view price history. Do you want to know what the best price is?
Latest coupon and price update (UTC):
Banggood ($11.99)
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood. Is it a reasonable price for this item? It’s a good price, isn’t it? The average is $15.89.
Link: Banggood product page
Price: $11.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/feV
Old coupons (from the oldest to the newest): BG662cb9
(you can check these old coupons out, but these probably won’t work)
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.
Price history and price alert
Do you need price history chart (for all/most countries) for Tuya WiFi Smart Carbon Monoxide Detector? There we go. The lowest price was: $9.99.
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)).