The S3 Image Optimizer is a WordPress plugin that will allow you to optimize all your images in 1-1,000+ Amazon S3 buckets and optimize them using the EWWW Image Optimizer. If you are using WP Offload Media, you may not need S3 IO at all. This plugin is generally for folks who use other solutions to put their images on S3. But, if you have 20 sites sharing an S3 bucket, or have lots of buckets, and you would want to optimize them all from one place instead of 20 different sites, this is the plugin for you.
Please see the Installation & Usage instructions to setup the S3 Image Optimizer.
Hey, guess what? We released S3 Image Optimizer to the public on WordPress.org, so you can now download it directly from the built-in plugin installer or the new plugin home page.