I use dafyomi.co.il in yeshiva and they made a neat english summarization of all of shas. If u could make their content optionally download to be viewed alongside the daf, it would greatly enhance the user experience. (The website states that as long as the leilluy nishmas is left w/ the text, they don't mind anyone distributing it.) Lastly, there is a ton of other content (like charts for every daf and quizzes too) that can be utilized as well. If you haven't already, be sure to check them out.