Temperature loggers can be useful and vital in many places. For instance they can be implemented on greenhouses, freezers and other sensitive environments where temperature changes can cause trouble. Temperature logging can help finding weak spots in the system and help prevent failures in future. Some time ago temperature loggers relied on internal storage devices, where temperature data along time stamps were saved locally that later had to be loaded in to computer to visualize data. Today when internet of things services are here, logging can be done online without need of storing data locally. You can see logged data instantly, set alerts and even remotely control hardware. The only thing that is needed is constant internet connection. This is also not a big problem, because connecting to internet is easy as never. Whole logging system with WiFi can be set up for less than $20. noelportugal shared his simple demo on how to build a temperature logger that would send data to thingspeak.com which allows free connection to your device.
Set up consists of Arduino Pro Mini 328 which reads temperature data from 1-wire DS18B20 temperature sensor and sends it over WiFi using ESP8266 module. WiFi module can be interfaced via USART. With Arduino library this task becomes really easy. Once you get your data online, it is up to you what you want to do next.