SMS Alerts

Hi all, I want to setup SMS alerts for my members but a little unsure of how to do that. I know that you can send a email to a cellphone by putting the mobile number and @cellphoneprovider.??? but that sends an email to the cell phone. Can someone point me in the right place for sending SMS alerts to my members?

I am wanting to create this plugin specifically for my site but not sure how it works.

Michael