iPhone Apps and Custom Tab Bars
There’s been a new trend with iPhone apps to use more sophisticated custom tab bars. In case you don’t know what a “tab bar” is, it’s historically been the black bar at the bottom of the screen, which provides the main navigation for the iPhone app.
A trend started by Instagram (the first popular app to place an action button in the tab bar, not a view selector) is quickly expanding to other apps like Gowalla and Path. While I recognize this isn't exactly ideal from a UI ecosystem standpoint (it break several of Apple's interface guidelines), I do think that sometimes disruption is necessary as it leads to innovation. The problem is, many developers just wait for Apple to innovate.