Twitter has launched a functionality that allows new users to sign up to the service from a third party website or application.

Twitter has created a new ‘Sign-Up’ API (application programming interface) which will make it possible for anyone to create an account when away from the site. The new Twitter Sign-Up API has not been released publicly, but it has just found its first implementation with popular online local guide Citysearch.Businesses with profiles on Citysearch which create Twitter accounts using the new API, will have their tweets appear on their Citysearch business page.

“Potential customers can make smarter decisions with the fresh information being shared with them in real time,” Twitter wrote on its blog, “and businesses can manage closer connections with audiences across the Web.”

The API also has shades of a future Twitter business model.

Businesses keep looking for new ways to integrate with Twitter, but the launch of the Sign-Up API with Citysearch may be one of the most important integrations yet.