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Click here… to search for Xiaomi RTCGQ02LM Human Body Sensor on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (18.69 USD): BGSmart6
(CouponsFromChina.com tip: 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
Old coupons (from the oldest to the newest): BG15SH12, BGSTHO15, BGXMNEW02, BGXMHSG, BGXMHUSOR, BGHONEY2110, BG218307, BGSHOM15, BGSHE15, 13f142, BG0f6d3b, BGce29b8, BGCL887, BG6c8cbc, BGba1eee, 6GSGIT, BGD11037, ADMITAD2212
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for Xiaomi RTCGQ02LM Human Body Sensor is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).