I was very interested in the concept of flip teaching and decided to try it with..... freshmen! Yikes! I was elated to find that their Geometry text came with its own set of 2-5 minute videos per section. This was phenomenal. In order to be able to evaluate whether or not each student was watching the videos and learning anything, I used the notes from the videos to make Video Notes sheets that students filled in as they watched the video. At first, some students didn't bother to do them, but these were the same students who either do not do their homework or will say they have "attempted" it but a closer inspection reveals something contrary.
I mostly used it for introductory sections or sections containing lots of definitions. It was a classroom time-saver! and allowed us to do the application problems in class.
All in all, I have been very pleased with this strategy and will continue to use it. It has also helped me in developing my "remote school" plans.