Wish I could help, unfortunately I am just chiming in also, in hope of any pointers to extra docs, examples, etc.
After an inordinate amount of searching documentation and forums here, and the web at large, I was really surprised to find stunningly little in terms of skeleton code examples, anecdotes, or useful information in general. At one point early on I came across what I now remember as a sample project basically consisting of stubs to use while testing. Unfortunately I didn't mark it and now can't find it again - and am beginning to wonder if I just dreamed it or something.
I would dearly love an example project that did nothing but display a broadcast setup UI extension, either from the view controller template XCode creates, or from an associated xib or storyboard - the extension doesn't need to do anything but show up. My test extension either shows a blank popup with none of the controls (which can't then be dismissed) or nothing at all depending on whether I use the template code as is, or change the plist to use a storyboard. I'm also now getting an "Access denied" error code 5801 in the non-stuck case, but I think that is seperate since I'm getting that when I cancel a mobcrush broadcast too, not just the test broadcast extension
In neither case do I see any console prints that indicate *any* of my extension executed at all - not viewDidLoad, loadView(), awakeFromNib() (thought that would happen in the storyboard case, for instance), etc.
I fully expect I'm just missing something that should be obvious, but some demo code would sure help.