An in-app approve or deny payment feature is one of the things I’m most looking forward to building. I hope we can implement 3D secure in that way but I’m not sure.
In theory we could even settle payments between a merchant with a Mondo account and a Mondo user outside of the card networks which should reduce the price of … well, everything … by about 1% and combat fraud more effectively. The user would enter their email address / mondo user ID / some identifier on the merchant page, then the merchant would make an API request to us, we’d send a push notification to the user, the user would confirm with their thumbprint, we’d send an API request back to the merchant and they’d complete the checkout process. 
Of course that only works once we have enough users to make this worthwhile for merchants so we’re focusing on that for the moment 