Ardwolf via Amazon offers its Ardwolf Mini Smart Plug for $18.75. Coupon code "7YQJ8ZQQ" cuts it to $15. With free shipping for Prime members, that's $4 off, a buck under last month's mention, and the lowest price we could find, outside of the mention below. It works with Amazon Alexa and Google Home and allows you to control devices with Android and iOS apps.

Note: Futurebuy21 via eBay has it for $12.55 with free shipping, although it ships from China and may take up to five weeks to arrive.