Cameron Lock, of Yammer fame, describes the complexities involved that led her and the team to a simpler, more modular approach to the mobile application design. The most important bit after grouping everything into modules, practically, I think, is this:
We stopped defining margins between modules. Instead, all the spacing in the app would come from padding within the modules — specifically, top padding. Bottom padding would have worked, too; just not both. The key is to choose one of the two and stick with it.