Alex Eames took a (cheap as chips) Wemos D1 mini (which has an onboard ESP8266 wifi chip), connected it up to an analog temperature sensor and then flashed a script to the board that would send the sensor readings to a Raspberry Pi. The Raspberry Pi runs a PHP server and a script that accepts the data and displays it to your web browser, logging it out to a CSV file at the same time. He’s written the whole thing up as a tutorial with all the code and you can take a look at it here.