I know I've seen something like this on hackernews before. SaaS for taking over the IDE at any point of a recording, just without the video.
EDIT: https://news.ycombinator.com/item?id=28207662
Seems this but with a slightly different spin?
EDIT2: Gave it a go. Works as intended, so good job on that.
The video being a video, makes it a bit awkward though - if I stop the recording and edit some part, I'd want to see the changes live, but for that I guess I'd have to start the server myself? And when I hit play, my changes got deleted anyway (?).
As for the usefulness aspect, personally I am not sure that this has a benefit over e.g. watching youtube tutorials/following books. I watched one of the videos and I'd have to concentrate on the video, the text and audio at the same time, and it wouldn't be me typing the code anyway, so I'm not sure how much I'd remember of it. I'd have to stop, open a new project and try to rewrite it myself to memorize the concepts deeper. But that's just my personal take - might be that there's a big userbase for such interactive learning!