Human Made announced the release of Tachyon, their open-source scalable image service. It integrates with Amazon S3 and can be used with or without WordPress. When it does work with WordPress, it integrates with the Tachyon plugin and Human Made's S3 Uploads plugin. It's built in Node.
Ryan McCue in the article goes into details of the how and why behind Tachyon. It's neat that Tachyon is structured in such a way that everything works independently; for example, you can use other CDNs with Tachyon.