I do this slightly differently:
I setup a Google Voice account and use a ruby script on the Intermapper server (as a notifier) to use the GV account to send an SMS to any arbitrary phone number. (Probably limited to USA numbers due to GV restrictions.)
Pros: Works when your email server is down as long as you have internet; doesn't require knowing email->SMS address for numbers (eg. <phone>@vzwtext.com).
Cons: Requires working connection to Google Voice.