Jakobodb

This utility plugin changes the theme of the current user to Sunrise, and uses the Sunrise color scheme when browsing the front-end, to help ensure you are viewing and editing the Development Site when making crucial changes to a site.
This plugin also adds a menu item to the admin bar to further confirm that you are on the Development Site.

Development Mode

Uses Sunrise theme on Dashboard and Frontend to visually represent development mode

Matt Cohen

WP Hook Finder is your assistant for developing on top of an advanced parent theme, theme framework or high-end WordPress plugin. Hook Finder scans a theme or plugin of your choice and lets you know of any custom actions or filters that have been added and which functions hook on to which actions or filters.

WP Hook Finder

Scan a WordPress theme or plugin for functions that are attached to hooks and filters and for any custom actions or filters that are added by the code …

Development Mode vs WP Hook Finder