On his blog, Dorigo goes deeper into his predictions for the iWatch, explaining that a 2.45-inch iWatch with a Retina display of 480x640 would have same pixel density (326 ppi) as the iPhone 5s, the iPhone 5c, and the Retina iPad mini. He's speculates on what a 2.45-inch iWatch's UI might look like, with the creation of several mockups with an iOS 7-style design.
While several rumors have suggested the iWatch will indeed run iOS, it is still possible that Apple could go in an entirely different direction with the device, creating a standalone interface or an iOS-based interface that deviates from the iPhone's interface.
Dorigo suggests that 80 pixels of the screen might be reserved for a CarPlay-style digital home button, leaving a 240 pixel space for apps, but that's pure speculation -- Apple could also choose to place a physical home button on the side of the device.
Along with a home button built into the screen, Dorigo imagines a largely touch-based interface, where Siri is activated via a press on the screen and individual apps have large, easy-to-press buttons. He also speculates on what the interface might look like when connected to an iPhone, as the iWatch is rumored to be heavily integrated with existing iOS devices.