A link at the top would suffice. Or the bottom. Or anywhere, really, that doesn't prevent me from viewing the content I was trying to view.
Edit: In case it's not clear, I think the article is written about full screen overlays that I'm describing. If not, I'm all wrong here and my posts probably don't make sense. I'm totally cool with a site mentioning that they have an app and that I should get it. What I'm not okay with is when you are prevented from accessing the site until you agree or disagree to get their app.