Me too. Since they have an API, it would be really nice if someone could make a WordPress plugin.
Kraken Image Optimizer: https://kraken.io have a WordPress plugin, in case you're interested. It additionally optimizes GIF images.
That is an awesome plugin. Thank you for posting this. I wouldn't have known about it otherwise. I'm working on an extremely image heavy site and this is perfect. It even lets you chose between "lossy and lossless" compression.