(Duplicate of this question, but I figured I could try again, since that one wasn't answered...)
The UISearchBar on the iPhone has an option showsSearchResultsButton. When you turn it on, it shows a button with horizontal lines inside the search bar, and you can implement a callback that will be called when the user presses it.
The thing is, I can't find a single place on the Internet where it says what the intended purpose of this button is. I know I could make it do anything, but I'd like to know what it's actually for. Should it show a history of searches, or all items without filtering, or what?