Just wanted to mention this. I came to learn of new tool and project called Appium recently. It uses Selenium WebDriver API to wrap Mac iOS UIAutomation, allowing you to test native apps using Selenium API.
It's still in infancy but a promising project.
I think it would be a nice tool to integrate with Robot Framework. It might already work with Selenium2Library out of the box. And if not, perhaps someone can port a version to be Appium compatible.