The Altmetric application is currently installed for all Scopus users by default but will only appear in the sidebar when there is data available for the article that you're currently viewing. You can find it underneath the "Related Documents" box on the right hand side of the screen.
What does Altmetric do?Altmetric watches social media sites (e.g. Twitter, Facebook, Pinterest, Google+), science blogs, many mainstream media outlets (including the NY Times, The Guardian, non-English language publications like Die Zeit & Le Monde and special interest publications like Scientific American, New Scientist) and reference managers for mentions of academic papers.
It cleans up this data, enriches it and then allows authors, readers and researchers to see it in context.
Though not every article is discussed in public online Altmetric tracks over a hundred thousand mentions a week. Well worth a look alongside the regular bibliometric SCOPUS functionality.