We were developing a monitoring tool for a website and we thought it would be nice to send a text message along with the email alerts if it went down.  I found this link that provides the information that you need to send a text message from a mail server. 

http://www.livejournal.com/tools/textmessage.bml?mode=details

For example to text message a sprint pcs phone you would set the email address from your app to the format below:

yournumber@messaging.sprintpcs.com

Just make sure to set your mailformat is set to plain text and your message most likely can't be over 160 characters.  This may be old news to some, but this is very helpful since we live in a world now where we need to be notified pretty much instantly about things.

Note: you can also test by just using a normal yahoo, gmail, work email, etc... and send an email to the proper address depending on your provider.