http://docs.moodle.org/dev/Moodle_Mobile#Requirements:
Moodle 2.4
Future versions will require the last minor versions if Web Services are not backported.
The iOS native app degraded its features if some web service functions were not existing (get_site_info) on the Moodle site but were required by an app feature. I think the HTML5 app should degrade nicely too whatever it is a missing feature on the device (camera/audio) or in the Moodle site (web service function). Can you confirm if it's the case Juan?