To send an SMS from an Android app, it's recommended to use a backend application that implements the Twilio REST API and wraps up your credentials. This approach avoids storing sensitive information directly in the app, reducing security risks. The process involves creating a backend application using Java and the Twilio Java library, setting up ngrok for external access, and then developing an Android app that makes HTTP requests to the backend to send SMS messages. The Android app uses OkHttp to make requests to the backend's URL, which is obtained from ngrok. By following these steps, developers can create a secure and scalable solution for sending SMS messages in their Android applications.