The Calypso desktop app lets you manage all your WordPress.com and self-hosted WordPress site that uses the Jetpack plugin, in one place. No need to login to your WordPress admin to manage or add content, you can do it from your desktop, it will direct you to your backend for you to edit your plugins.
Using Calypso I can manage all my sites from my desktop, I can publish new content to any of my WordPress website’s from one place, no need to jump to each websites backend to add content.
Calypso moves WordPress.com away from MySQL and PHP, the new WordPress.com is a browser-based client for WordPress API, you can build any other application on top of it, using WordPress as your backend.
If you are a developer you can check out Calypso from the GitHub repository. Calypso is open-source and WordPress invites developers to fix or add something new, you just open a new pull request with your changes.