Passport is said to be a mobile first web page. It is on th beta page at least. Basically the 'APP' would then likely be a front end trimmed browser - the kind you natively do with forums and the likes that make an 'icon' on your homescreen. Looks like an app, feels like an app, is a small webpage.
Sounds like that wouldn't load without a data connection though – eg. if you're one of the thousands at Rhythm & Vines and the mobile network is slammed. Or if you're on a plan with no remaining data etc.