Sharing Data Between Apps on an iDevice

Is it possible to share on-disk data between iOS applications, or are they truly sandboxed? In other words if I wanted to make a shared repository of data to be accessed (and/or modified) by one or more of my apps, could it be done?

One of the listings on the iOS features page is "Share Data Among Apps", but is this what I'm looking for, and what are the related APIs?

Googling hasn't turned up much else in this area and I know I can construct a path to just about anywhere in the iDevice directory structure. Would it be against Apple's TOA, leading my apps directly to rejection, or is there hope for such an architecture?