There's good news and there's bad news.
Unfortunately, the video feed cannot be accessed Webviews of apps such as Facebook, LinkedIn, native SMS app on Android, Twitter or WeChat, or when saving the app to home screen. The video feed is accessed through getUserMedia which is currently not available in these WebViews.
However, with 3.0.0 you can implement single image mode. If the webview has access to the native camera (parent app permission dependent), then you can decode from a single image captured via the camera.