It's based on the work by Lazar Lazslo (the JS port of the ZXing library : https://github.com/LazarSoft/jsqrcode)
As you see, it's possible to recognize a QR Code captured byt the User Media plugin.
The demo showcase the recognition of a Sprite containing a QR Code (for example generated by my other plugin : QR Code Creator), but you can also recognize a snapshot taken from the webcam.
It works on FF and Chrome (surely on Opera and Safari desktop too, but I haven't tested it on my machine, I don't have a recent build of those on that one).
The demo : https://dl.dropbox.com/u/1412774/QRDecodeDemo/index.html
The plugin : https://dl.dropbox.com/u/1412774/QRDecodeDemo/pode_qrdecode.1.0.zip
The .capx : https://dl.dropbox.com/u/1412774/QRDecodeDemo/QRDecodeDemo.capx
QR Code for this page :