From the developer's website :

"Every fifteen minutes, my server will check the Tube status and send any delays to the relevant Twitter accounts. You can then quite easily subscribe to individual Tube lines and get updates via whatever means you deem appropriate as you would as a Twitter user.

A neat side effect of this is that there is now Atom and RSS feeds for each Tube line which you can subscribe to and get these updates sent directly to your RSS reader too. Twitter can also serve as a historical home for Tube problems from now on.

This is real Tube 2.0 stuff.

Bakerloo: tubebakerloo

Circle: tubecircle

Central: tubecentral

District: tubedistrict

East London: tubeeastlon

Hammersmith and City: tubehcity

Jubilee: tubejubilee

Metropolitan: tubemetro

Northern: tubenorthern

Piccadilly: tubepiccadil

Victoria: tubevictoria

Waterloo and City: tubewcity

How to use: Sign up for an accont with Twitter. Once you are logged in, go to the Tube line profile that you want to add and choose “add” in the right hand menu. Check the delivery settings on your Twitter homepage to make sure that status updates are delivered through the right medium (over the web, over IM or over SMS).

I can’t promise it’ll always work. And I’m sure there’ll be a few little bugs which might appear over the next few days. Things like planned closures (the W&C line doesn’t run at weekends, and I may need to tweak the script in order to not tell you that). If you get updates which you don’t want, I apologise in advance and I’ll try to make sure that such annoyances are kept to the minimum."