VDmitryV

This plugin allows developers to use the WordPress WYSIWYG editor for their own 
fields during plugin/theme development, for example – for Custom Post Types. 
Code is based on WordPress the_editor code.
Sponsored by GlobalBases.com GmbH WebBases & WebSoftware http://www.globalbases.com
PLEASE NOTE: Plugin is in alpha stage of development, so don’t expect it to be fully working. Don’t expect anything.
Known limitations: working only on post create/edit pages

WYSIWYG Helper

Plugin for developers that want to use WYISIWYG in their plugins/themes.

Abrar Ahmed

This plugin is particularly designed for developers so that they can easily upload images via URL.
Features of this plugin: 
1. You can give URL to this plugin then this will upload the image to WP and will return attachment ID. 
2. You can give the same URL multiple times but it will not upload an image each time, it will upload an image once and will return attachment ID each time when it is called. 
3. If image URL is change or size of the image on URL is different then just on that condition image will be uploaded to WordPress
It has some more functions too that will help developers for getting details about image and size as well.
<h3>Arbitrary section</h3>
The following features of this plugin are going to be defined for developer understandings.
<h3>A brief Markdown Example</h3>
Unordered list:
<ul>
<li>Function iUploadImageByURL This function is the basic function that can be used while upload image from URL. It will return Attachment_ID after creating an attachment from image URL. Image from URL will be uploaded once if URL and size of the image are same. If the same URL with the same size of the image given then already created attachment of that image will be uploaded.</li>
<li>Function iGetFileSize This function can be used to get the size of the image from URL.</li>
<li>Function sFormatSize This function will return measurement format size of the image.</li>
</ul>

URL Image Uploader

This function is a tool for developers to help them upload images from URL to the WordPress site.

WYSIWYG Helper vs URL Image Uploader