TP-Link Wifi Switch and Outlet

TP-Link Switch $39.99 - $7 Amazon Coupon = $32.99

TP-Link Outlet w/Energy Monitoring $38.92 - $7 Coupon = $31.92

These are not directly compatible with SmartThings. They do however integrate directly with the Amazon Echo. They have been integrated with a secondary server here:

Also there has been a comment that these may get future integration: