In my iPhone application work, recently one issue came up. It is separating an iPhone application that I am developing into two applications while sharing custom data (i.e., images and text files) between two applications. So, I googled several forums with this issue. Here is my findings.
1) Using a server as a storage
2) Using a URL scheme
3) Using the pasteborad (UIPasteboard)
3) Using an "Address book" area
None of these was appropriate for my project where I need to share several images (1600x1200) and text files on a device without connection to a server. So, at this moment, I conclude that there is no way to share custom data between two iPhone applications.
[Reference 1] [Reference 2] [Reference 3] [Reference 4]