At&T has an excellent service for producing speech sound files. It is free for private use. This is really nice to use with alerts as you can create customized speech sound files in seconds and then integrate them with your own alerts. That way when an alert fires, you get an exact message of what just happened.
As an example, say that you have an alert that fires when RSI crosses 30 from below. You can create a sound file that literally says: “Hey, RSI just crossed the 30 line from below. Get to work!”.
The link to the site is below. Its pretty self explanatory – you simply type the text into the box and click download. You can then use that file as the sound file for your alert.