A Moodle HQ directed Mobile app is being planned and you can see it’s preliminary development page at http://docs.moodle.org/en/Development:Mobile_app. This development effort seeks to flesh out the main usability features (using icons to help guide users) and functionality which will bring Moodle use via mobile phones to the next level (and in a place where the community can contribute, suggest and vote on new features and code).
Compared with some of the already available Mobile Apps for Moodle (http://moodlenews.com/mobile) the official app looks to engage the device’s inherent tools more deeply in order to upload audio, video and images from a mobile handset directly to Moodle, allowing for mobile-specific activities and assessments. Support for the other standard Moodle features is also implied.
The wire-frame mock-ups of the screens look promising and it looks like a great plan. I hope it comes to fruition. To keep up to date on Mobile development for Moodle check out the forums at http://moodle.org/mod/forum/view.php?id=7798.