Using Asterisk to Dial and Talk with Festival

[Chris Carey]

Some of you may have seen one of these web sites before where you can
type in a phone number, and a message. When you submit the form, a
server will call the phone number and say the message.
I want to implement this with Asterisk + Festival.

There are a few technical hurdles to figure out in doing this. The
first is - I'm not sure how to get Asterisk to "do something" after
dialing.

You have the Asterisk function Dial(), but as far as I know, execution
of the dial plan will not move past that line until the call that was
dialed is terminated.

I can successfully use Festival to talk to someone when they call me:

Answer()
Festival("You must beat me in trivia before I will ring the phones")

But I have not been able to do:

Dial(some number)
Festival('Hi, Im calling you!!')

Does anyone know how this could be accomplished?