RestKit (http://restkit.org/) is working on something similar. Right now you have to manually push your data back to the REST service, but in version 0.11.0, they are going to add exactly the kind of functionality you're looking for:
Yeah, we've written our own REST framework also which is actually surprisingly similar (and small, ~1k lines) to AFIncrementalStore which does all the things I mentioned except in a leakier abstraction completely outside of the CoreData store. It works well, but it pains me that there isn't a cleaner way.