Very good app, jazakum Allah khairan, the audio recitation is very good, the "تشكيل" is a plus, some suggestions : bookmarks, search, and hadith email (to share it with others)
For English: transliteration & audio (option of display: only English, English plus Arabic & transliteration together)
Jazakum Allah khairan for your great effort
Hani about An-Nawawi's Forty Hadiths