When you're busy localizing macOS applications, you will often have to switch the system language and region settings. This is usually done in the System Preferences pane
Language & Text, but it's not too handy. So I have created my own little tool which offers the most important information from its Language and Formats tab views in a single window.
I have also added some the UI tweaks often used by localizers.
Enjoy this free app. I love to get your comments.