Dragon Naturally Speaking 10 is actually quite good, and has very little setup time. However, the fact that it took until version 10 to get to the 'quite good' area should tell you something about how hard is to make. Development started in 1980, and the first commercial version showed up in 1990 for $9000, then version 1.0 of 'naturally speaking' in 1997. It took a LONG time to make. Admittedly, they were starting from basically scratch, but still.
There is another program that uses the DNS10 engine, showing that it can be 'plugged in' to something else, but it's somewhat expensive, and I doubt it's an easy task.
The point of this post - it's kind of unrealistic with the current state of tech.