I created this plugin for my wife's website, Katie Crafts. I recently moved all of my sites over to Hover and Digital Ocean respectively, which offers an AMAZING deal for a $5 VPS, but they only start off with 20GB hard drives.
While that may not seem like a huge deal, her site is quite photo-heavy so this helps me keep an eye on things and will alert me if too much space is being used. If that happens, I can hop over and fix the situation by making her server larger or cleaning up some space in the uploads folder.
I wanted something simple and easy to use and I really thing I hit the nail on the head with this one. I genuinely hope this plugin helps you even half as much as it helps me -- I had a lot of fun making it. Enjoy!