There are times in your IOT projects when you want to send notifications of certain interesting event, example intruder detected. Sending an SMS is one such mechanism.
There is an excellent service called Twilio, but it is a paid service.
Enter Telstra (they are always there to help!) . It has a free limit of 1000 SMS messages a month. Sweet!
Register, then create an “app” in their backend, this will give you the “API Keys” you need
You first make a HTTP request for an authentication token (OAuth2)
With the token in hand, you make another HTTP Request which sends the SMS.
Introduction and Setup here
User Guide here
My Code for Python here
My Code for NodeRED here
My NodeRed node for Telstra SMS API here