The Vonage Client SDKs for Android, iOS, and Web are used to build voice and messaging capabilities into applications, with the Conversation API helping to showcase their multi-platform functionality. The V-App is an end-to-end application on all three platforms, built using Node.JS as its backend client, which handles RTC webhook events from Vonage and stores them in a Postgres database for efficient querying. The V-App supports user accounts, conversations, calling, sending images, and more, with the backend client also having a voice answer route that returns an NCCO. To deploy the backend seamlessly, the Vonage CLI Scaffold Plugin can be used to download, setup, and run all three clients and the backend, making it easy for developers to try out the V-App.