According to the documentation, there doesn't seem to be any examples of using external images or external videos (i.e. from YouTube).
I was wondering if anyone knew if it was possible (like this)
<Video style={{
width: 3.0,
height:2.0,
transform: [{translate: [0, 4, 5]}, {rotateY : 180} ],
}} source={{uri: 'https://www.youtube.com/watch?v=vPCoxAlfFsw'}} />