There is an iPhone/iPod/iPad app called “My Moodle” which provides mobile device access to Moodle 2.1+. See http://itunes.apple.com/us/app/my-moodle/id461289000
The experimental Moodle 2.1.2 site at AIAI now has mobile web services enabled as required to support this app – they are off by default. See http://docs.moodle.org/20/en/Enable_mobile_web_services
My initial attempts to snap a screen shot image with an iPod and upload it via the My Moodle app indicated the file exceeded the maximum upload file size, yet the PNG file involved was only 44KB… and our site is set for upload file limits of 8MB to 128MB depending on what layer is filtering.
A future road map for development of the My Mobile app is available. See http://docs.moodle.org/dev/Mobile_app