This SEO plugin is automatically generating an overview about the keyword densities of the used keywords and 2-/3-word keyphrases in the pages / posts content. 
The statistics will be updated in a specific interval while the author is writing the text in edit-post and edit-page dialog. 
These informations have informational character only – no meta information will be inserted into your blogs pages. 
You can use the meta keyword suggestion at the bottom of the statistics to copy these informations into the input fields of your favourite SEO plugin. 
Stopwords for different languages can be filtered out of the text before the keywords densities will be calculated. 
The keyword density checker tool is a branch of the <a href="http://www.keyword-statistics.net/wordpress-plugin.html" rel="nofollow ugc">keyword statistics plugin</a>. 
If you don’t need the meta stuff the keyword density checker is much faster – no code will be executed on ordinary pageviews. 
The additional code is needed in page-/post-edit mode of admins and authors only.
Features of the SEO-Tool:
<ul>
<li>Automatic calculation of the keyword density for single keywords and keyphrases (2- and 3-words) while writing the content</li>
<li>Meta keywords suggestion depending on the pages/posts content</li>
<li>Language specific stopword lists</li>
<li>Optional filter for stopwords</li>
<li>Update interval for the statistics generation can be changed and switched off</li>
<li>Generation of statistics for 2- and 3-word phrases can be deactivated</li>
<li>Definition of the default language and stopword filter status for authors</li>
<li>Prevent authors and contributors from changing the content language and stopword filter status</li>
<li>Uses nonces for plugins security</li>
</ul>
Integrated stopwords for:
<ul>
<li>Brazilian Portoguese</li>
<li>Bulgarian</li>
<li>Czech</li>
<li>Danish</li>
<li>Dutch</li>
<li>English</li>
<li>French</li>
<li>Hungarian</li>
<li>German</li>
<li>Polish</li>
<li>Slovak</li>
<li>Spanish</li>
<li>Turkish</li>
</ul>
Backend translations for:
<ul>
<li>English</li>
<li>German</li>
</ul>
Read more about this SEO plugin on <a href="http://www.keyword-statistics.net/wordpress-keyword-density-checker.html" rel="nofollow ugc">keyword density checker</a> – <a href="http://www.keyword-statistics.net/de/wordpress-keyworddichte-plugin.html" rel="nofollow ugc">german</a>

SEO-Tool – Keyword Density Checker

This SEO-Tool provides a keyword analyzer calculating the keyword density of the page/post content and generating statistics for keywords and phrases.

A completely new version of this plugin is available and it allows to use the latest Polymer components: <a href="https://wordpress.org/plugins/wp-polymer/" rel="ugc">WP Polymer</a>
This plugin allows to add Polymer elements (v0.5) to your posts and pages, the same components used in Android Lollipop. You can use the HTML editor with the Polymer tags directly or the shortcode [poly] for all the elements. The correct HTML libraries will be loaded automatically. 
Polymer website: http://www.polymer-project.org/
Notice: Polymer is still in developer preview, some constructs may change in future. A modern browser is required to run Polymer web apps.
Features
<ul>
<li>Polymer tags directly available (core & paper) in posts / pages with the HTML editor;</li>
<li>[poly] shortcode to access all tags;</li>
<li>simple widget;</li>
<li>auto import the necessary HTML components;</li>
<li>code blocks to easily manage elements;</li>
<li>Javascript editor in posts / pages admin;</li>
<li>CSS editor in posts / pages admin;</li>
<li>import iconsets options;</li>
<li>autop on/off option;</li>
<li>template override on/off option;</li>
<li>documentation links for each tag.</li>
</ul>
Shortcode
[poly ELEMENT-TAG ELEMENT-OPTIONS]
Tags: core-icon, paper-button, paper-checkbox, paper-slider, etc.
Options: style, id, class, etc.
Examples
<pre><code>[poly core-icon icon="favorite"][/poly]
[poly paper-checkbox][/poly]
[poly paper-button raised style="color: green"]A green button[/poly]
[poly paper-item icon="home" label="Test link"]<a href="http://www.google.it" target="_blank"></a>[/poly]
</code></pre>
Notes
<ul>
<li>code blocks allows to create elements and import them directly from the Polymer box in posts / pages. They allows also to load JSON data, see FAQ for an example</li>
<li>autop option: the autop() WordPress function adds p and br tags to the contents when a newline is found, but this can break the Polymer tags. This option allows to enable/disable autop() in posts / pages (plugin default: no autop)</li>
<li>template override option: if this option is enabled this plugin will load a special template which provides only the required components to run a Polymer app. This is useful if you want a “fullscreen” Polymer app</li>
<li>to create RESTful apps try JSON REST API (WP API) plugin. See FAQ for an example</li>
</ul>

SEO-Tool – Keyword Density Checker vs Polymer for WordPress