Hi! What about next feature - custom search engine? If user selected a word or some text, he can do his research only in Wikipedia or local dictionaries.
With custom search engine user could choose the source of information (youtube, google, online dictionary etc). And if the result of research will appear inside the app it could be great!

P.S. With that feature this nice app will be more comfortable and unique, because I didn't saw this feature in PDF Expert app, for example.