HTC Desire Z :: Way To Set Text To Speech Engine For Notification Sounds?

I would like to set up custom notification sounds for the various apps (email, message, FB, etc.). I would prefer that instead of using the various cute sound effects that come with the phone, I want to have a voice that says, "new email" or "new message" instead of the various beeps and chimes. Ideally, I would like to use the text to speech engine that comes with the phone to do this like what the Navigation app. How can I set up the notifications to activate the text to speech engine to say a certain phrase? If that is not possible, how can I activate the text to speech engine to say a phrase and then save the output to a sound file which I can then select as the notification for those various apps?