This project is nothing special! 
However, it is pretty simple to make and can be helpful to monitor the temperature around you with your ESPboy and a cheap temperature sensor.
It all started from a discussion with a community member on Discord (@vr_user). I turned a few small tips at the start into a finished application for the ESPboy. @RomanS wanted me to keep track of this application on the forum, so here it is. 
If you have an ESPboy, whether it was sent to you by Roman or you built it yourself, you should know that you can easily connect various modules and sensors to it to extend its capabilities by using the pin rail available on the header that on the top edge of the console, just above the screen. Roman already proposes some exciting projects to do yourself to exploit this extension bus. Here is another one.
The idea here is to connect a simple temperature sensor (Dallas DS18B20) to follow the evolution of the measurements at constant intervals on the screen:
I refer you directly to the page that describes the project, where you will also find the source code of this application, available on GitHub:
Enjoy yourself!