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.