Now that we are close to the release of the new Moodle Mobile app I've created some docs about the general architecture and how to develop plugins:
http://docs.moodle.org/dev/Moodle_Mobile
http://docs.moodle.org/dev/Moodle_Mobile_Customization
http://docs.moodle.org/dev/Moodle_Mobile_Plugins_Development
Also, here you have the github repository if you want to take a look to the source code:
https://github.com/moodlehq/moodlemobile
If you have Javascript and/or HTML5 mobile apps skills, your feedback will be really appreciated
PD: Notice that this is still a work in pogress, so some things may change
Regards