Late last year, ITEAD launched Sonoff Micro WiFi USB switch that allows you to turn on and off USB powered devices over WiFi using eWelink app for Android or iOS. It integrates with Amazon Alexas and Google Home, and does the job, but people who like to use the open-source Tasmota firmware will be disappointed to learn it's not based on ESP8266 processor hence not compatible.
Luckily, there's another option: Sinilink WiFi USB switch (aka XY-WFUSB) based on ESP8266 WiFi SoC, and supporting up to 20V/5A according to the manufacturer. It is currently sold for under $5 including shipping