Hi Gareth,
The Mendix server will not help you to do video streaming. Streaming and forwarding live video is a complex solution and could probably not build from scratch but should use a 3rd party solutions that can be integrated in your app.
There is already a module for this in the App Store. https://appstore.home.mendix.com/link/app/113742/ and https://appstore.home.mendix.com/link/app/109621/
To implement this in the Native module you might need to some effort.
http://blog.zenof.ai/create-a-react-native-video-calling-app-using-twilio/
Or use the web view widget https://docs.mendix.com/appstore/modules/native-mobile-resources , might give you an quick escape to embed some HTML
To learn how to build a widget for the native apps, you could follow this tutorial https://docs.mendix.com/howto/extensibility/build-native-widget
Cheers, Andries