I am assuming your Objective C project is for an iOS-based device such as the iPad or the iPhone, correct?
Indeed, we show mobile/tablet devices when we talk about PI Web Services because web services in general are a good approach to interoperability. They may be not as pervasive as HTML is, but it empowers development in a very wide range of environments and languages.
Turns out, Apple left out the implementation of a simple interface to web services in their iPhone and iPad SDKs... Luckily, the developer community came up with a few solutions that they shared with the rest of the world.
As you may know, the current version of PI Web Services provides SOAP web service endpoints (by opposition to RESTful endpoints). As such, you could try searching the web for something like "SOAP web service objective c" - I did that a few times in the past and my research led me to 2 implementations that seemed to be the most popular out there:
I'm sorry if that represents a little more work that what you were expected at first, but Apple really didn't make it easy to develop with web services...
Looking forward to reading about your progress! Hey, maybe this could be a good [DEAD LINK] community project... ;) Anyone?