Thanks for the module, I have always needed something like this and used .htaccess to do it. A module would be great.
Now, my problem is the following: I have installed Shield dev version on a Drupal 7 minimal and perhaps misunderstood something along the way, but the result was that the site was blocked. The username and password I introduced in the configuration did not work.
I could not get in. I had to delete the module by hand on the server. I tried Chromium and Rekonq and no difference, site blocked. I would love to provide more details and try this again, but there is no info in the logs of Drupal, and nothing noteworthy in the logs of the webserver.