Wordpress Twitter Access Control
A wordpress plugin that requires visitors to follow you on twitter before they can see anything on the site.
Checkout the code and upload it to a folder inside the wp-content/plugins/ folder.
Create yourself an explaination page that users are directed to to require authenticate. This should include an explaination of whats about to happen, and why. A "sign in" button is automatically added to that page.
Edit tac-settings.php with a consumer key and secret for the twitter app you want users to authenticate against. Fill in the required variables, following the comments in that file.