Should be possible.
In theory, you could simply listen for every single key on that keyboard.
The thing that is currently unworkable though, is getting the browser to interface with any input device that isn't a keyboard or a mouse.
There's already a draft for MIDI support though (http://www.w3.org/TR/2012/WD-webmidi-20121025/) and someone has already laid some groundwork for MIDI keyboard integration.
SO yea. No native support for MIDI keyboards yet, though this might change soon and then it really will be just a matter of implementing simple event listeners (if at all).