Here's an auto-attendantee example of how you could write a form based application:
Imagine you own a heating and air conditioning company, and you want your phones to work like this: When someone calls into your shop, you want the phone to be answered with your company greeting. It says "For faster service, please enter your home telephone number. " If the phone number matches a current customer, find the owner right away on his cell phone, home phone, whatever. If the phone number doesn't, bring it to an operator or to voice mail. With a form based application, that's maybe a few hundred lines of VxML and PHP, a $500.00 computer, a SIP infrastructure.... and that's it.
Here's to irony... I signed up for google ads, and it places adds up there that relate to what I'm writing about. But, everytime I criticize Asterisk, it puts Asterisk ads up there!