You can send SMS messages to mobile phones by email. Every major carrier also has their own email domain.

• AT&T: 1234567890@txt.att.net
• Nextel: 1234567890@messaging.nextel.com
• Sprint: 1234567890@messaging.sprintpcs.com
• T-Mobile: 1234567890@tmomail.net
• Verizon: 1234567890@vtext.com
• Virgin: 1234567890@vmobl.com

Use the full number, including the country code. And keep it to 160 characters. The T-Mobile works great. I use it to get text messages whenever the web server gets automatically restarted due to some problem. Works a little too well, if you know what I mean.