I rolled my own using python and apache and asterisk call files.
The code I pasted here handles the dial-on-answer side of things, you can easily change it up to do a transfer to an internal extension instead.
For the dialing, I used python instead of php since we’re creating files on the file system, and it’s got more flexibility there. I have a daemon process that is configured via a web interface to parse a MySQL database, build the call files, and move them into the outgoing queue.
There might be more sophisticated solutions out there, but it’s pretty effective and robust.