I have the impression the alarm(d) framework on the N9 is quite different from the N900. In that case I would opt for a new app and not spend too much energy on a port attempt.
You were just a few clicks away If you click on that page on first link to alarmed 0.3.0-1, then on "Source: alarmed 0.3.0-1", you will find http://maemo.org/packages/source/vie...armed/0.3.0-1/ There you can download tar.gz with sources and debian packaging rules