Today, Ars Technica reports the release of Remember The Milk (RTM) for iPhone. Ars suggests that RTM has remained one of the most interesting and innovative apps for keeping track of tasks. Existing primarily as a rich web app, RTM integrates with a virtual boatload of other apps and services, including Gmail, Windows Mobile, Google Calendar, Twitter, and now, iPhone.

Just like the website, RTM for iPhone allows tasks to be added quickly to an Inbox to get them out of your head where they can so often be forgotten. If you want, you can add all of a task’s pertinent information right away, such as a priority, due date, notes, tags, and even a location. When it comes time to get things done, the beauty of RTM (and similar GTD-based systems) is that you can view your tasks by almost any criteria: list, due date (Today, Tomorrow, This Week), tag, location, and more. Adding a task while viewing a specific list or due date will endow your new task with those criteria.

Ars asserts that one of RTM’s most useful features, especially in light of the iPhone’s continued lack of an alert system for third-party apps, is its rich support for reminders. While you can’t apply a custom reminder time for each task, the RTM site offers a wide variety of options that can be sent over IM (AIM, Google Talk, Skype, and more), SMS, e-mail, or even Twitter. You can chose to receive a daily list of tasks and set a site-wide reminder time for tasks with a due date, all of which can be sent over any of the aforementioned communication methods. These reminders aren’t quite as integrated with the iPhone OS as Apple’s phantom push alerts system or a true background process would be, but they certainly offer a lot of flexibility for staying on top of tasks, no matter how or where you work.

RTM for iPhone has a lot of other interesting tricks, such as Smart Lists that can aggregate tasks by any criteria, horizontal support for using the iPhone OS’ wide keyboard, multilingual superpowers to run under every language the iPhone OS supports, and, of course, customizable syncing with the RTM website (auto, WiFi-only, manual), and much more. Like the other apps for BlackBerry and Windows Mobile, though, you’ll have to upgrade your free RTM account to the $25/year Pro account in order to use this application.

Be sure to check out Ars Technica’s full article.