Sure @techapj can you look into how difficult this would be? Not sure if Oneboxer being an external gem (I kind of regret this tbh) complicates matters.
Related: I looked at Google tag manager recently and saw the following;
Published on 8 Sep 2015In this weeks video we’ll look at how to track Embedded YouTube Videos with Google Tag Manager. We can do this by implementing a custom HTML tag which listens for the interactions on the video. This allows us to monitor events such as a user only watching 25% or 75% of the video, as well as how many times they hit play or pause. We can then visualise this data in Google Analytics. Please see our first link if you want the written tutorial used in the video, enjoy!
This is fairly complicated and quite minor since majority of people just play inline. count of plays would be way more interesting but that is even more complicated.
When people have messed up their embed and leave a link for video sometimes the numbers vary wildly and it’s a really good indication to my users of popular/unpopular content which is lost if you can only see the preview.