I recently received an Amazon Echo Dot.
After linking all the regular things like Spotify and Google calendar, I then moved on to finding how I could link a Raspberry Pi or some of the ESP8266’s that I have lying around.
I came across the following GitHub page (https://github.com/kakopappa/arduino-esp8266-alexa-multiple-wemo-switch) which allows the setting up of an ESP8266 as a WeMos device, this allows you then setup your ESP to use the GPIO to control a relay such as an Optocoupler
Initally I used a dev ESP8266 to control the LED mounted to the board, the GitHub package will setup the ESP8266 as a web server that the Amazon Echo will treat as a WeMos plug device. You can then use commands you have set to turn on / off devices
Here's a video of the LED control on the dev board:
I decided to connect the relay to control the lights on my fish tank as they are tucked away so that kids can't get to them.
Below is a video of the finished setup, controlling the fish light (white) and the fish moon light (blue):