"...Anyone in the US can receive Tweets on their phone even if they haven’t signed up for Twitter..."
"Fast Following without creating an account is currently available only in the US...
"...From your computer, wherever you see a user on Twitter.com, you can hover over their name or avatar, and click on the phone icon that appears in the hovercard. Whenever they tweet, you'll get it as an SMS message on your phone."
For example, in the United States of America, if you want to follow me text the message "follow slick" to 40404.