Control APP: eWelink.
Price history, coupons and price alert are available on this page. 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 no active coupon in my database right now (for Banggood).
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): elec, e2bcea, SONOFF15, BGE13, 13f142, bGpAnDacHeCk, BG9NY, BGVDay10%off, BGMPB2020, BGTT10, bGhOnEy10, BGSMOFF, BGSONOFF15, BGELIG0920, BgcLuBofErtA10, BGSONOFF16, BGAFF10OFF, BGSTHO15, BGCuponation10, BGHONEY2110, BGSHOM15, BGSHE15, 6GSGIT, BGSmart6, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BGJUNEGSG9, BG15Sonoff, BG8b589f, Cuponation9, BGHU2320, 9OFFSUMMER, BGXIFD222
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – SONOFF Dual Channel DIY WIFI Switch [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for SONOFF Dual Channel DIY WIFI Switch. The lowest price was: $7.99.
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)).