Featured app from Chapter 4 of "iPhone in Practice" by Bear Cahill published by Manning Publishing.
Dial4 displays your address book by name (or number if no name) and lets you filter by typing in the last 4 digits of a phone number in the search field.
You can also search by other blocks of digits: area code or exchange.
Chapter 4 of "iPhone in Practice" takes the user step-by-step through creating this app including: UINavigationController, the Address Book, UISearchBar and launching a call.
Learn more at: http://brainwashinc.wordpress.com/iphone-dev-book/