As @Spocki says, there's that tutorial showing how to do it with SMS text messages.
Realistically all you need to do is use the same wiring, but use the code from https://www.espruino.com/SIM900 and you have an internet connection that you can send data over.
It could be as simple as running something like this:
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
As @Spocki says, there's that tutorial showing how to do it with SMS text messages.
Realistically all you need to do is use the same wiring, but use the code from https://www.espruino.com/SIM900 and you have an internet connection that you can send data over.
It could be as simple as running something like this: