I've just added self voicing to the Windows viewer.
Here's an example.
I launch SL from Visual Studio, walk up to an object called "Healthy" who chats to me. Everything he and I write in chat is spoken.
I also demo clicking the object, to which it responds with a chat and also issues me with a notification which is also spoken.
I got my inspiration for this test from the following films,
You can purchase this product from SL Exchange