Xiaomi Mijia Wifi Remote Controller Switch (Banggood, Aliexpress: Power input 5V—1A, Infrared frequency 38kHz, Color Black, Wireless connection Wi-Fi IEEE 802.11 b/g/n 2.4GHz, Working temperature -10 ° C ~ 50 ° C, Net weight 133g, Product size 100x 100x 26mm, Product material PC (the best price with coupon)).
You can create price alert here, copy coupons and view price history. What is the best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
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.
Link: Banggood product page
1. ($17.99): bGhOnEy10
2. ($17.99): BGSS10%SW
3. ($18.99): 13f142
you should apply the coupon 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): 502C6B, 6C8E66, 6c9903, bgmh2, BGMIB2, BGOMG2, TS15prime, TISPrime01, BG14XM, PICODICOM, BGXMSSR, BGBFAFF2019, BGCITYADS2019, BGMRC, BGRCRA, BGMHPK, bGpAnDacHeCk, BGOMG4, BGRCSRA, BGHOMEAPP, bgshOOp10, BGHome15%, BGHOMEAPP13
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Mijia Wifi Remote Controller Switch. The lowest price was: $13.59.
Price records source(s): Gearbest, 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)).