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?
That looks like marketing speak. The only way to share data locally is to pass it in the URL when launching another app. Otherwise, you need an internet server based solution.
Another thought: can you use TCP locally between apps with the new multitasking support? Apps like Air Sharing are allowed to create listening sockets.