Hi. Is there a globally recognized developer certification for Objective C? any tips on what would make me marketable in objective C/ Mac OS X/ iPhone development?
I'm going out on a limb here, but you might want to develop some objective C apps for osx and iphone.
Certifications mean very little -- simply understanding the language and knowing how to apply it will make you marketable. If you really want to impress an employer, start working on your application portfolio and show them something real, not just a piece of paper that claims you know what you're talking about.
stackoverflow is good platform to show, by answering questions, how knowledgeable you are as an iOS or a Mac OS developer.
Creating an iPhone app and selling on the app store is another option.
Contributing to OpenSource iPhone/Mac OS projects is another option.
It's called the app store. Have a popular app there, and you're marketable.
I agree with all. Your calling card are the products you have produced. A paper certificate means little without a portfolio of work.