My JSON-RPC Framework for Cocoa is now available here!
It will allow you to query your JSON-RPC WebServices using a simple but very flexible API in Objective-C:
For more info (about error handling when network down, etc.) and methods documentation, see the doxygen documentation, available as an Xcode docset. (you will have to pull it from git to open it in Xcode or Safari)
This framework supports both JSON-RPC v1.0 and v2.0
(see JSON-RPC’s official website for more info about JSON-RPC)