The guiding principle behind the Unix command line lurking underneath the GUI of every Mac you own is a collection of simple programs that co-operate to enable you to achieve complex tasks. That co-operation part is missing from iOS, due to tight app sandboxing, but the idea of simple, small apps that do one thing well is very much alive.
The latest from this school of design thought is App Cubby's $0.99 app, Timer. It comes highly recommended -- with a 4.5-star average review in iTunes and featured-by-Apple App Store spot. I almost don't need to explain the functionality; a screenshot alone may be enough, although there are some neat, subtle touches that don't immediately meet the eye.
