From within a Unity (game engine) app running under iOS I invoked authentic YouTube app's uploading view by simple doing this:
Applicaiton.OpenURL("http://youtube.com/upload");
Let it not scare you that the deeplink looks like a URL. It still invoked the native app and not goes to Safari.
It's all good and works perfect however I need more control. I need to precompose the movie's title, description and most importantly skip the movie selection view but point YouTube to a specific file.
Are there more arguments/parameters in YouTube's deeplinking scheme?