How to integrate blog status?

You can use the option API to set the blog_status and then display it. If you want to use blog description for the purpose you already have the UI available to set it from Setting->General and set the tag line to update your blog status.

Then you can display the tag line anywhere in your theme template using the following:

echo get_option( 'blogdescription', 'Default status message' );

But if you are using blog description somewhere else and want a dedicated option for the blog status purpose then you can use the update_option like in the examples below to set and display the blog status.

To set the blog status:

update_option( 'blog_status_message', 'This is pretty cool blog status message' );

To display the blog status:

echo get_option( 'blog_status_message', 'The default status message' );

For more information on Options API.