Media Center Communicator is a great way to control your Media Center PC just by voice. I have been using it on my PC for a while now and love it.
There was one thing that didn’t work for me, I use the Xbox 360 as an extender and couldn’t control it with MCC. Well One Voice have released version 3 with Xbox 360 support, so I can control my Xbox 360 Media Center just with my voice. V3 is also designed for Vista Media Center so it looks great to.
Best of all is that you can try it for yourself for free!
Plus One Voice offer mceSpeechTools available for licensing:
mceSpeechTools allows third party development of speech recognition commands into new or existing Windows Vista Media Center and Windows XP Media Center Edition 2005 applications. From home control to online music services, mceSpeechTools is easy to integrate for developers to enable the creation of voice commands for applications ranging from setting thermostats, changing lighting, viewing security cameras or even purchasing music or videos online
V3 is available for Windows Vista Home Premium and Windows Vista Ultimate for $79.95
Try a demo version and watch a video demo at http://www.sayittoplayit.com