From the Moodle News site, a table with links for Moodle mobile apps that have been reviewed (on the far right). I am using Mbot for Android, and so far it is a pretty effective way to at least view what is going on in your Moodle courses.

As more and more students get Smartphones, the numbers of students who are taking their Moodle quizzes or posting to Forums from their phones will increase. Online instructors: you may want to get ahead of this curve and suggest to students which apps work well, and what functions you feel can effectively be accomplished on a phone. On the other hand, if a student writes an “A” assignment, all on his or her tiny virtual keyboard, who am I to argue? With choices comes freedom as well. Here’s the apps chart:

http://www.moodlenews.com/Mobile/