What are some alternatives?
When comparing Optimus.io and CodeKit, you can also consider the following products
ImageOptim - Faster web pages and apps.
TinyPNG - Make your website faster and save bandwidth. TinyPNG optimizes your PNG images by 50-80% while preserving full transparency!
Transmit - Transmit is an FTP client for Mac OS X and Mac OS Classic (which is unsupported).
JPEGmini - JPEGmini - The Photo Optimization Tool Trusted by Tens of Thousands Image Perfectionists
pngquant - command-line utility and library for lossy compression of PNG images