Moodle 2.1
Expected release date: 1st July 2011
http://docs.moodle.org/dev/Moodle_2.1_release_notes

Moodle has been developing their own iOS/Android app.
In 2.1 improved support for Mobile themes and browser detection (does require Moodle server admin to change some settings or set options).
http://docs.moodle.org/dev/Mobile_app

"Licensing
The iPhone/Pad apps will be free from the iTunes app store (with FULL functionality). However the source code will be owned by Moodle Pty Ltd and will not be initially distributed under the GPL. One possibility is that we will help produce custom-branded versions of the app for specific Moodle institutions that want it.

The Android apps will definitely be GPL and free for download and modification by other developers. This is in keeping with the philosophy of the Android platform and will allow the community to innovate on that platform."

Moodle app 1.0
Requires Moodle 2.1 (released 1st July 2011).

There is something to consider in looking at the brainstorming that's been collected about the moodle mobile app. as quite a few items listed mentions the ability to upload either a photo or a video - this could lead to viewing issues by Teacher (depending upon how teacher accesses the course - with similar hand held or laptop).

Might be time to setup a YouTube Channel of your own and provide an extra field in user profile for the channel screen name.  It is also time to revisit/consider what document types teachers are using … Word Docs and PowerPoints which might present issues to Mobile users (it always has, but now might come to the forefront of planning and training for teachers).  Much depends upon the Mobile device abilities … can mobile device view a Word Doc/PPT?  How about a PDF (exported from Word/PPT)?

Take a gander at mBook (developed by Moodle HK):
http://www.moodle.hk/file.php/1/2011/mBook126.mov

iPhone only … no Android app.  According to those sites that track data on devices it appears Apple is leading in tablets, but Android is leading in smart phones.  It is time to survey students concerning their personal tech (their smart phones).

mBook claims to support most contributed modules - but am sure that is in reference to version 1.9.x of Moodle

Due to massive change in code/behavior, etc. it's IMHO that ISD's might be better off starting over as opposed to attempting upgrade of a 1.9.x (highest) to a 2.1 in place.  One of the additions to 2.1 is the ability to import 1.9.x (highest) course backups into 2.1.  If that IS included in 2.1 and works, then one could start running a 2.1 site.

TIP: Moodle Networking works between versions. Significance: IF some teachers have used and care to continue to use add-ons for 1.9 that have not made the trip to 2.x, those teachers courses/content could be found via a MNet link from 2 to the 1.9.x course.