trogau

You can query core, plugin, and themes individually, or check all at once.
It defines four new methods:
<ul>
<li>xmlrpcCoreUpdateCheck – checks core, returns true/false</li>
<li>xmlrpcPluginUpdateCheck – checks plugins, returns true/false</li>
<li>xmlrpcThemeUpdateCheck – checks themes, returns true/false</li>
<li>xmlrpcUpdatesCheck – checks all of the above, returns an array of trues/falses.</li>
</ul>
The plugin was created primarily for WPUpCheck (http://trog.qgl.org/wpupcheck/), a simple 
Windows application that remotely polls a WordPress site to see if updates are available.

XML-RPC Update Check

This plugin provides XML-RPC methods for checking the update status of WordPress websites.

Minor

Today it’s really important to have everything up to date (security, compatibility, new features and performance). Default WordPress setting is automatically install just minor core updates and languages.
No settings required. Just install and active this plugin and your WordPress (including plugins and themes) will be up to date.
You can focus on the other things than updating your WordPress, save your time!
<h4>What will be automatically updated too?</h4>
<ul>
<li>Core</li>
<li>Themes</li>
<li>Plugins</li>
</ul>

Auto Updates

The best one of auto update plugins. If you don't agree with me - write a review, please! :-)

Simple, light, easy and no ads

Does exactly what is needed without any extra bloat. Thanks!

Perfect

I checked the code of this plugin before installing it: it does what it says and absolutely nothing else.

It basically just adds the minimum code to enable the auto-updates within WordPress. There is absolutely nothing else in there, which is awesome.

Install this plugin and rest easy it's not bogging down your website like 99% of plugins out there.

Extremely Lightweight and Does What it Says

Let WordPress to automatically update his core, plugins and themes - silently in the background.

XML-RPC Update Check vs Auto Updates