I am probably the last person in the world who figured out only now that you can sign up to follow a Twitter account without creating a Twitter account.
You just need to do is SMS "follow [username]" (without inverted commas) to +447624801423 - US number has a shortcode.
A good explanation of how it all works is here:
Why am I so excited?
It means that charities can use Twitter as a free SMS updates tool. For example I am at a rally or at an event and I can sign up to get updates on what's going on on the other end of the rally or in negotiations about the issue we are rallying about, etc...
Updates would have to come from people who have Twitter accounts and are friends with the main account (the one that people are following)
Things to investigate....
1) If someone who follows me anonymously (which is what happens to people who sign up in this way) when I publish "me and friends" RSS feed - if they sent an update to the twitter number - will it show in this feed?
Because what you really want is to be able to use twitter in both ways as a broadcast tool but we could also ask supporters to post a message to a politician via Twitter SMS. This is then published as an RSS feed with everyone's messages (again me and friends feed) on a charity blog or website as well as on the Twitter page.
2) Can you set up a shortcode that would go to the twitter number? Is it possible to have many shortcodes for one mobile phone number/SIM card?