This is somewhat language/framework independent, as it mostly has to do with providing an XML
"entitlements" configuration file (which goes into the application bundle) and
code-signing your binaries/bundle.

http://developer.apple.com/library/mac/#documentation/Security/Conceptual/CodeSigningGuide/

For instance you can grant your application the right to read/write files as
specified by the user (via file dialog). From the Apple docs:

"Any time an application running inside a sandbox invokes an NSOpenPanel or
NSSavePanel dialog, rather than showing the panels directly, AppKit
automatically asks the Powerbox to present the dialog. From a developer
perspective, there are no code changes required in terms of how these panels are
used; this process is fully transparent."

So as long as Qt/Mac would use NSOpenPanel etc. properly there should be no code
changes required - in theory!

In practice I found out that Qt crashes as soon as I request a (native!) file
dialog. Details here (unfortunately I received no answers yet):

http://lists.qt.nokia.com/pipermail/qt-interest/2011-August/035597.html