iOS: Due is a simple iOS app that manages your tasks, alerts you when their due date has arrived, and also provides you with simple, re-usable "egg timers" for time you need to schedule right away.
Although not a feature-rich app, Due elegantly handles your daily tasks within an elegant interface. You can set tasks for any specific time and Due will make sure you remember to do them. After they've complete and the due date has past, Due will archive them into its Logbook. Between your active tasks and logbook are your egg timers. You can set the duration and name them, then re-use them as needed. The egg timers are especially useful if you're a fan of the Pomodoro Technique.
These are the basic features of Due 1.1. Due 1.2, which will be a free update, adds a whole bunch of extra customisations. You'll be able to auto-snooze on your to-dos, set secondary alerts, account for time-zone shifting, set repeating reminders and more.
While the price is a little on the high side for simple functionality ($4), Due is a really solid app that handles the few things it does really well.
Due ($4) | iTunes App Store