Another proof-of-concept is Amazon Fire TV which have a very good "Voice Search" feature which shows how voice command adds accessibility to the search function in a media player
Such more advanced speech recognition in "Voice Search" could maybe work online via Google Speech API, Siri, or a offline speech recognition library to enter text into search
As another cool proof-of-concept and for ideas checkout is the "Jasper" project which is user-friendly "ALWAYS-ON" accessibility platform and open source Python-based implementation that uses CMU Sphinx (
http://cmusphinx.sourceforge.net ) , and even though the current Jasper client is not designed for XBMC it is nice as a proof-of-concept, and since both Jasper and CMU Sphinx is quickly becoming a popular community driven frameworks for other to develop always-on, voice-controlled applications project, you too could create a "Jasper Client" for XBMC using that upstream Jasper client code
http://jasperproject.github.io/
https://github.com/jasperproject/jasper-client
There is also an non-Python voice control open source software for controlling XBMC on Linux that is called called "xbmcvc" (short for XBMC Voice Commands) which also uses CMU Sphinx for voice recognition, same as the Jasper project
http://forum.xbmc.org/showthread.php?tid=123621
https://github.com/kempniu/xbmcvc
xbmcvc send the commands via XBMC's JSON-RPC API so perhaps could get some ideas from it as it already supports XBMC navigation and playback commands
xbmcvc supported navigation commands; UPWARDS, DOWNWARDS, LEFT, RIGHT, SELECT, BACK, HOME, CONTEXT, WEATHER, PICTURES, TV, VIDEOS, MUSIC, PROGRAMS, SETTINGS, FAVORITES
xbmcvc supported player commands; PLAY, PAUSE, STOP, MENU, PREVIOUS, NEXT, SHUFFLE, UNSHUFFLE, REPEAT ALL, REPEAT ONE, REPEAT OFF
Note however that there are actually no Python-based addons/plugins that add voice command to XBMC, only separate voice command applications that can send commands to XBMC, none of which are cross-platform, and no one that is close to being as simple to install as an addon, and no one that is even particularly simple to use with XBMC.
Otherwise I think being able to install (if so separate) simple Python-based addon/plugin for XBMC/Kodi that can use a such voice command API in XBMC/Kodi is a valid subject to discuss here as an idea generally improve accessibility.