David Satime Wallin

BMRE Domain Monitor is built to keep an eye on the domains you add.
It checks the expiration date and warns you if a domain will expire in 30 days or less (both through email and in the admin interface)
It also has the feature (optional) to suggest domains that are similar to the ones you’ve added and that are still available.
DISCLAIMER: Do not ONLY trust this plugin for your domains. It works well but I can not be held responsible if something should go wrong and your domain does actually expire.
LICENSE:This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
<pre><code>This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. </code></pre>

BMRE Domain Monitor

This plugin is meant to monitor your domainnames and warn you before they expire.

Nimbus Digital

Redirects http://somedomain.tld to http://someotherdomain.tld
Assuming you have 2 or more domains in use for a single WordPress site. This plugin forces the use of only one no matter which is entered in the address bar.
If, for some reason, your host won’t automatically redirect from one domain to another, then this plugin will do it. It checks the URL used to access the site and does a 301 redirect if incorrect.
In theory htaccess should do this, but in my case it didn’t. Perhaps because I am using domain aliases (or CNAMEs) and I wanted to insure that the main one was always in use, even when accessed using old links.

Force Domain Redirect

Forces your Wordpress site to load on the domain registered in the WP admin.

BMRE Domain Monitor vs Force Domain Redirect