Streaming xbox to phone via xbox app

All Xbox games are 16:9. You are seeing a rendered stream from your Xbox or Xcloud. Few if any support the wider ratio due to low installed base and major performance hits that the extra resolution introduces. If you want 21:9 gaming you ahould look at
PC for more robust support.

With a hdmi or via streaming via xbox app

I'm sorry, But at this time only the master account that purchased the subscription can use cloud gaming.

Your son can stream the local console you own to his phone via the xbox app

Personally I use the twitch app on my phone and computer to watch people's stream. I haven't really tried to watch via console. I hope they fix this problem so people would be more enticed to watch streams on their Xbox because that sounds like a pain!

I agree. If not via Smartglass then via a native Xbox Movies/Music app. Why pay $9.99/mo only to stream via the Xbox in your living room when you can subscribe to Pandora, Grooveshark, or some other service that will let you stream music on any device. Or
Netflix in the case of movies.

I'm sure you can do all of these things on Windows Phone, Surface, and Xbox. But not on other platforms like iOS and Android. Hopefully Microsoft addresses this soon. I wonder if their competitor's app stores will try to block such apps though since Microsoft
is competing directly with their own content services.