Sometimes you just don't want to get off the couch and walk to the caller ID display. Your Linux server understands and wants to help.
My first exposure to synthesized speech was on a Commodore 64; the speech demo took an eternity to load off a floppy diskette, and the speech sounded like an English as a Second Language student was speaking it directly into a pillow. Today, with DSP and decades of additional speech programming research in the bag, synthetic speech is much more passable, and folks are constantly coming up with novel uses for it.
In Detroit, I have a buddy whose Linux server used to announce logfile entries and tell him when the doors around his house were opened and closed. While this speaking server was mysteriously silenced right around the time he got married, I still love his hack. Adapting speech capability around Asterisk is a logical use for two of my favorite pieces of open source software: Asterisk and Festival, the University of Edinburgh's speech synthesizer. With a little bit of dial-plan configuration, your Linux Asterisk server will be announcing your incoming calls in no time (and announcing a whole bunch of other stuff, if you want).
Mac OS X users will find that Festival is similar in some ways to the
Say command on OS X, though Festival provides much more functionality to Asterisk than
Say does. For example, you cannot use
Say to speak to callers, as you can with Festival.
First, you'll need a sound card ...