Integration between versions of the same book.

I want to start reading a hardcover book, scan the last page read with my phone, and continue from the same page with an e-book or audio reader.

I also want to scan a paragraph in a translated paper book, and get the original version of that paragraph. Or a translation, if I am struggling with an original version.

For language training, it would be useful to have an audio book that can repeat the previous sentence. Or start from a point I click in the text. (The latter is available in the edX videos: I can have a transcript rolling beside the video, and I can position the video by clicking in the transcript.)