I guess the question pretty much says it all?
And I would prefer not to access cloud services such as Microsoft Translator and Project Hawaii?
Is there any direct API I can access?
(For metro apps)
I was able to get the Microsoft Speech Platform working on my Windows 7 laptop (both Voice Recognition and Text-to-Speech). You just need to install SDK and the runtime. You can also download additional Voice and Language packs. I would think it should work on Windows 8 as well. Here is a good sample on how to set it up to recognize some basic phrases like "Find restaurants near Seattle".