SwiftNinjaPro

A Plugin That only allows whitelisted IP’s, or optionally whitelisted browsers, to access wp-login. 
This plugin does Not effect front-end login plugins. 
If an IP is not whitelisted, the wp-login page will be killed and replaced with a message saying “your IP/Browser is not whitelisted”, or optionally redirect the user to 404 page instead.
A better way to hide wp-login. You can add a list of admin IP’s to this plugin, where you want to allow usage of wp-login. 
Even if you have other users that login, its better to use another plugin for a more secure front end login, and this plugin will only allow a specific list of IP’s to access the wp-login page. 
You can also (optionally) have this plugin attempt to redirect anyone to 404 page, if they try and access wp-login without the right IP. 
You can also choose to disable the 404 redirect, and instead tell users there IP is not whitelisted, and that they should contact the admin if this is in error. 
The plugin does Not block wp-admin, so once logged in, you can still edit your site on the go. 
The plugin also has an option to whitelist your favorite common browsers to wp-login. This means you can keep users from accessing the wp-login page, simply because there using Internet Explore, and not what you chose to allow. 
There is another option (which may return false positives), that attempts to check if the source of an IP is commonly used by a proxy server, and can block proxy IP’s to try and reduce spoofing.

WP-Login and WP-Admin Whitelist

A Plugin That only allows whitelisted IP's, or optionally whitelisted browsers, to access wp-login, or optionally wp-admin.

jamiewilson

Gatekeeper allows administrators to take a WordPress site offline quickly and easily while leaving it fully accessible to administrators and other authorized users. Site visitors will be shown or redirected to a specified offline page. An optional blacklist can be used for permanent bans.
** Features **
<ul>
<li>Visitors can either be redirected to an existing non-WordPress offline page (using http 302 temporary redirect) or WordPress pages can be temporarily replaced with the offline page.</li>
<li>Logged in admins can be whitelisted</li>
<li>The current admin’s IP address can be automatically whitelisted</li>
<li>An IP-based whitelist that can accept specific IP addresses, wildcards, and ranges</li>
<li>A basic IP-based blacklist that redirects blacklisted IPs to a specified page (not to be used for security)</li>
<li>A notifier that appears on administrator pages when the site is offline</li>
</ul>

Gatekeeper

Gatekeeper allows administrators to take a WordPress site offline while leaving it accessible to authorized users for maintenance, testing, etc.

WP-Login and WP-Admin Whitelist vs Gatekeeper