The GSM Shield also includes a Telefonica SIM card that includes a worldwide data tariff which can be used anywhere there is a cellular signal.

SMB has unveiled a new open source Arduino SMS switch box and gateway they have created called the SensorMessageBox, which is Arduino compatible and provides a simpler way to control SMS messages ...

The program could interface with Arduino through a serial port, and send data to Python, which in turn forwards it to your phone.

The shield can be configured to send GPS and sensor data from devices attached to an I2C bus to remote servers, or a really cool COSM server.

If you've mastered the art of Arduino, but haven't yet been brave enough to toss in a bit of GSM communication, the how-to guides linked below definitely deserve your attention.