Software apps and online services
While organizing stuff in my lab, I found my Adafruit FONA module. It is a SIM808 cellular radio. You could build your own cell phone or 2G data device. So I grabbed my Hologram.io SIM card and embarked on sending MQTT messages to Adafruit.io. The payload? GPS coordinates.
If you're new to cellular modules and AT-Commands, you might want to check out my detailed blog post.