Features include the ability to have the Arduino send an SMS message when a sensor or data set reaches a specific threshold, or even send and receive voice calls directly to your Arduino based ...

That is because the Arduino is just sending tiny movements, each of which is a code that represents a nybble (4 binary bits) of data.

They used the webaudio API to send serial data to a remote Arduino. The hack uses a FET, a capacitor, and a few resistors. They didn’t quite build a real modem with the audio.

Arduino devices have had the option of a GSM linkup for awhile, but getting that cellular link to truly strut its stuff hasn't always been easy, even for those of us who'd be inclined to program ...

Particle’s Electron is a “cellular Arduino” with a global data plan ARM- and GSM-based board promises quick on-ramp for mobile IoT development.