The docs for NSURL state that:
An NSURL object represents a URL that can potentially contain the location of a resource on a remote server, the path of
What you are missing is the NSURLProtocol class. Takes about three dozen lines of code, and any code that handles URLs properly can access your in-memory data. Read the documentation, it's not difficult and there is sample code available.
Unfortunately there are some APIs that take an NSURL as a parameter, but can only handle file URLs.