PlayPosit Bookmarklet!
Bookmarklet:

The PlayPosit bookmarklet empowers you to add questions into nearly any video you find online with the click of a button.
Adding, the bookmarklet is as easy as dragging the icon above to your bookmarks bar. If you are having trouble with adding the bookmarklet to your browser, I recommend the tutorial that the folks at marklets made.
Now that you've added the bookmarklet, you add questions into the video by simply clicking the "Build with PlayPosit' bookmarklet you should see in your browser. For a list of video sources we recommend, check out the video sources we love. *
*by using the bookmarklet on a video you acknowledge that you have the rights to use the original video in your class