People will be chiming in soon enough saying that it’s possible indeed - though non-trivial - to “appify” an I7 game…
…but before they do, I’d just like to note that for iOS there exists an interpreter already, called Frotz, which - depending on your needs - may be simpler than “appification”.
On the other hand, if you’re asking whether I7 can be used to actually develop an app - the answer is no. It is used to develop I7 games (or works, or stories, or “abuses”); the ensuing file, though (.z5, .z8, .zblorb, .ulx or .gblorb) CAN be run in other platforms, including Android and iOS, as long as there is an interpreter installed.
EDIT - And what with Parchment and Quixe, it is possible to play I7 works in web-browsers, minimising the need for installation.