> You should be able to tap on a word and get a translation.
This functionality is available already on Kindle though :) you have the option of uploading your own dictionaries to it too.
That, combined with using https://www.clippings.io/ to manage highlighted text, makes the kindle an all round great tool for learning languages from books, or any text really. (you can use calibre to convert into and between most ebook formats)
I look forward to seeing where this goes! I imagine the really difficulty will be applying it to more than just German. Especially when you branch outside of indoeuropean languages