Man, I spent all day yesterday trying to reimplement the sensor for the ESP8266, as I thought it would be better to have it report over MQTT, but the damn thing keeps crashing in seconds. I literally cannot keep it working for more than a few seconds, no matter what I do.
I'm pretty disheartened, I'll try some more and either succeed or go back to an Arduino over serial... Do you have any experience with making it not crash?
Sadly, my ESP8266 experience is only about to start next week, I'm still abroad. But from the experiences of some of my friends, consider replacing the firmware on the ESP - some units were apparently sold with buggy one that made the module crash after short time.
https://github.com/skorokithakis/ArduiRC
I'll write up the details, but this is a good chunk of it.