Multimeters are nice and useful tools and you probably own at least one. Most of them have a large display to show the value, but no serial port outputting the measurements, making data logging tedious work as you have to write down the values yourself. You could invest in a more expensive multimeter with more options, but there are other, cheaper solutions as long as you are ready to spend a few hours on reverse engineering what you already own.

One way to add wireless logging capabilities to a Fluke multimeter was recently demonstrated by hardware hacker Sprite_tm on his website. Author of several Elektor articles on hacking, Sprite_tm, or Jeroen Domburg, explains in an extensive article how to connect an ESP12 module to a Fluke 15B+ multimeter in order to transform it into an online multimeter. The ESP12 together with the esphttpd library allowed Sprite_tm to add a web server to the multimeter that serves pleasing graphs of the measurements.