iOS 6 brings some welcome new features to the Phone app, including Remind me Later, which lets you safely avoid answering calls when it's inconvenient without having to worry you'll forget to return them later. As the name implies, Remind me Later ties the Phone app straight into the Reminders app, so it's really quick to use. Like the new, quick text-message replies, Remind me Later is accessible right from the Lock screen, and is only a swipe away.
iOS will now set an alarm and when one hour has passed, your alert will go off, reminding you to return the missed call.
iOS 6 also comes with a new Do not Disturb mode. If you're in a situation where you don't want to be bothered by calls for an extended period of time, don't want to have to dismiss them all manual, and don't care about being reminded to return them beyond the usual missed call notifications, Do not Disturb can be the better choice.