If you use Windows Media Center on your home theatre PC you can configure it to run via voice commands using macros for Windows 7's built-in speech recognition software. But just how far can you take that approach?
Gadget weblog Inspect My Gadget uses Windows Speech Recognition macros and AutoHotKey scripts to create voice tags that link with keyboard shortcuts. If you say "stop TV" it will send the keystroke Ctrl+S, for instance. The script used to make the system work waits for a predefined button press before listening for a command so that music or video dialogue cannot trigger a command. The button press also lowers the volume so that the system can recognise the user's voice from anywhere in the room. Finally, the author installed an arcade button in his recliner to trigger the voice command so no keyboards or mice are needed.
If you're interested in voice control this would be a good weekend project. Because the system associates audio tags with keyboard shortcuts you could also figure out a way to control XBMC using this method.
How-To: Voice control Windows Media Center [Inspect My Gadget]