Snoozr Aviator is a beautifully rendered, free alarm clock app for iOS. The author feels alarm clock apps have gotten too complex, so Snoozr Aviator makes setting an alarm a one-tap event. Tell the app what time you want to be awake, and then the software generates some alarms that vary in intensity until you reach your specified wakeup time. Most other alarms work the other way. They go off at the time set, and then you hit a snooze button as the time gets later and later.
The app lets you adjust the amount of snooze time if you like, or you can stay with the algorithms that the app suggests. The included wake-up sounds vary from subtle to more jolting. They're all effective without being grating.