I released a similar project on Github called Torpedo. It lets you schedule HTTP callbacks via a REST API.

    curl -X POST http://127.0.0.1:7931/api/callbacks/ \
    -d "url=http://example.com/messages/1/send/" \
    -d "eta=2012-03-25T08:00:00Z"

The above will call "http://example.com/messages/1/send/ at 8am on the 25th of March.

https://github.com/namsral/torpedo