A minimal firefox add-on to redirect requests to www.amazon.(com/de/co.uk) which seem to be the only domains supporting it to the smile.amazon subdomain but only if you're logged in.
This add-on checks for the amazon cookie and only redirects you to smile if you're logged in so if you're in a different container or a private window it will do nothing.
The add-on only requests the cookie permission to check if you're logged in and doesn't send data anywhere else. It's also open source so anyone can check the code or report issues at https://github.com/cgemici/AmazonSmileLoggedIn
