The Vonage Client SDK allows you to build applications for iOS, Android, and the Web that feature voice and messaging communications backed by the Vonage Conversation API. When building such apps, it is essential to consider how changes in connectivity can affect the app's experience, as devices switch between cellular and WiFi connections. The Client SDK provides listeners on Android and delegate functions on iOS to monitor connectivity changes, allowing you to update your app's UI to give feedback to users. The SDK also allows for automatic reconnecting of calls when internet connectivity changes, with options to recover a call if the app dies or move a call between devices. By using these features, developers can ensure a seamless user experience despite connectivity issues.