For information here is how you wire up the ESP-01;
and a pic of my setup;
I have also raised PR #8 with the changes I needed to make, just really adding the ESP-01 as a board for the project.
I am seeing an issue where it works for a while but then starts reporting key ‘1’ with a value of ‘0’ repeatedly very quickly. Not too sure if that is the EmonESP or EmonTX. I do have a Huzzah board so will give that a go and see if I get the same issue.