Hi, the custom branding of our apps (http://moodle.org/mod/forum/discuss.php?d=186546) can allow your users to purchase your course(s) on the iPhone by paying the "In-app Purchase". After the purchase of a paid course, they can enrol to that particular course.
If they access the same course on the computer browser, they can then be admited to the course too.
For further details, you can visit our site at http://massmedia.hk or contact me (james@massmedia.hk).