This post introduced the use of Twilio Programmable SMS with RxJS Observables in a Node.js application. It demonstrated how to perform repetitive API calls and emit responses using Observables, combining multiple inner Observables into one that emits data whenever an inner Observable emits new information. This technique can be used to get updates on the delivery status of SMS messages sent with Twilio Programmable SMS. The post also covered various additional resources for learning more about ReactiveX and JavaScript Promises.