To delete your completed tasks in Done, the to-do app from Chilli X, you have to rotate the iPhone to landscape view. This turns the screen into a single, giant orange button. Tap that button, and your iPhone or iPod touch emits a laughably loud laser-like zapping sound. Your completed items have been obliterated, sci-fi style.
As Apple prepares to celebrate a billion downloads from its iPhone App Store, I've been talking to some of those making a living from building mobile applications - and trying to work out whether the UK is developing an app economy.