With Twilio Media Streams, developers can extend their voice applications with real-time access to raw audio streams of phone calls. This allows for features like live transcription and simultaneous call monitoring. The code provided demonstrates how to handle multiple phone calls at once, differentiating incoming calls, tracking ongoing calls, and sending transcript data to connected clients. The application also includes functionality for subscribing to specific calls, displaying active calls in a list, and removing calls from the active list when they end. The example uses Node.js, Twilio, Google Speech-to-Text API, and WebSockets to achieve real-time transcription and streaming of audio data.