Ick. You've locked down this app so hard that you NEED two factor authentication, AND it has to be done from YOUR PROPRIETARY BROWSER. My bank doesn't have this much red tape. If you want to make this app any good, you'll design a way for users to sign in from the app and not from a proprietary web browser. You'll make the two factor authentication a SELECTABLE feature so that people can bypass it after logging in. This app is not worth the "headache".