I have implemented a wakeup call program on my Asterisk pbx. The extension works and when you put in the time it reads it back to you fine and everything. The only problem is that when the time comes around, there is no call.
This is the link to the page that explains the wakeup call program:
http://www.voip-info.org/wiki/view/Asterisk+tips+Wake-Up+Call+PHP
And this is the tar file associated with this page: