I found that I needed a smaller board, so I've shaved of about an inch of the PCB's width. It's now about the size of a standard Post-It.

 I've also added another 5V controllable output on IO17, since I need to use a solid state relay to power on and off a power amp. 

The Eagle design files and Gerber files are available in the Files section as MuffsyRelayInput2-Eagle.zip.

Improved software for the ESP32 is available on github. 

The ESP connects to your wireless networks and presents a web page with buttons to select inputs. It also has an HTTP GET API if you want to make your own web page for it.