Kite

Due to security/privacy concerns, JSON REST API (WP API) only allows post meta data (custom field value) for authenticated users. 
This plugin is an easy way to make post meta available when unauthenticated.
After activate the plugin, go to WP API Customizer option page. 
Click the plus icon to add rows. 
Set JSON attributes and custom field names in your posts that you want to use when unauthenticated. 
The JSON REST API will provide the data as “post_meta” like the following:
<pre><code>"post_meta":{"your_attribute_a":"Custom Field A value","your_attribute_b":"Custom Field B value"}
</code></pre>

WP API Customizer

Make post meta data (custom field values) available for JSON REST API (WP API) when unauthenticated.

mitcho (Michael Yoshitaka Erlewine)

Sometimes you have a need for having links to external URLs show up interspersed among your own pages or posts. This plugin lets you easily create such “redirecting” posts or pages by simply setting a custom field.
Usage: Add the custom field with label “redirect” to any post or page. Enter the redirect target URL as the value of that custom field. Now all links on your site to that post or page will be replaced with that redirect URL! If you try to visit the permalink URL for that page, it will redirect the user to that redirect URL too.
This plugin actually also works fine to redirect a URL to another URL on the same site as well.
Placeholders: New in version 0.9: the strings <code>%home%</code> and <code>%site%</code> in URLs are replaced by the WordPress home URL and site URLs, respectively.
Development of this plugin was supported by the <a href="http://arts.mit.edu/" rel="nofollow ugc">Arts at MIT</a>.

Redirect by Custom Field

Changes the URLs pointing to pages and posts which have a "redirect" custom field, using that entry as the URL instead.

WP API Customizer vs Redirect by Custom Field