I use a timer to track my work on these kind of courses.
Didn't think of looking for an API. But also, each course I've done so far has had a different structure, different number and length of video, different style of quiz/assignment, etc. So I'm not sure what metric would be most useful to beemind.
A complete aside: I've discovered that Coursera, edX, et al, also have courses in languages other than English. Usually complete with a transcript so that you can listen and read in unison.
I've been doing courses in French, which means that even if the subject material seems a bit basic, I'm still learning something useful. Highly recommend doubling-up: consume news or fiction or mooc in your target language.