Ok, not a full answer, but you can at least fire up the camera and upload images. Only tested on Chrome on Android, but I believe it works on all major android browsers. I also read that only Safari on iOS support this feature.
<input type="file" accept="image/*" capture="camera">
Try it here :
Click the button, you get a File Upload widget appear.
Click choose file and it opens the camera.
Not tried dealing with the upload yet in Anvil. When I get 10 mins … 
As for streaming … no idea, sorry.
Clone it here :
Also, I forgot about this :