I have been toying around adding WiFi to my CNC 3018 Pro with the help of an ESP8266 since my last video. This is merely a proof of concept, but it show it's definently possible for cheap! And this could be expanded to pretty much anything that has a serial connection, such as CNCs, 3D printers, anything Arduino controlled, etc.
It's done be using the serial connection to the external control pad, that my machine came with. In order to do that, it's just a matter of figuring out the pinout of the connector, hook everything up correctly, and remember to put a 3.3 volt regulator in line, so you don't fry your ESP-01 or whichever ESP board you are using. Everything from the original ESP8266 to more modern variants of the ESP32 should do the trick.
Again, the specific CNC 3018 Pro that I bought is the "Vogvigo CNC Machine Kit CNC 3018 Upgraded Pro Grbl Control Router Kit Wood Router Engraver 3 Axis Plastic Acrylic PVC Wood Carving Milling Engraving Machine" - https://amzn.to/2FzRYcr
You can get the ESP-Link software from Jeelabs here: https://github.com/jeelabs/esp-link