Huh,
In the Kiosk App Project - #2 by MarkHunte I am playing with, the last version posted can use a default webpage that is in the bundle and and uses the normal API to get the url.
The App is also able to choose a file from the finder??.
The returned url is in the form of "file:///"
I do not do anything special apart from having the url stored in the user prefs. Then picked up again by the WKWebView request from the prefs. ?
10.10 xcode 6.4