My provider, Rogers, has an online form to send SMS messages to my phone. I'm sure your provider has something similar. Just search your provider's webpage for it. Then all you need to do is write a simple (perl) script that's called by qmail to forward the email to your phone. The good thing about doing it this way, is that you can do checks on the email (spam checks, sender checks, etc).

Also, my provider gives our phones an email account (e.g. <phone number>@pcs.rogers.com) that your provider might also provide.

Adrian