Check out YourPND.com – they’re marketing a service that allows you to record your own navigation instructions to be used by a commercial navigation device. You can also have your spouse, a friend, or whoever else record the instructions. The service is currently only available in Dutch with an English version coming.
In his book Wired for Speech Clifford Nass points out that the type of voice (male vs. female, happy vs. sad, etc.) used by a speech user interface makes a difference in how people perceive the user interface and, by extension, how much they like and trust the device they’re interacting with. One key point made in the book is that people prefer voices similar to their own (this is the similarity-attraction effect). I’m not aware of any studies on how a user would react to a machine talking to him or her in the user’s own voice. How do people like such extreme similarity? I wonder if the YourPND people ran some user studies. If not (or if they’re not publicly available), this would be interesting to do.