Synology just released the 5.0 software, with chromecast support for streaming videos. So now I have my entire movie/TV collection on my Synology NAS, which I can pull up on my Nexus 4 and stream the video's on my chromecast. It has OTF bandwidth/conversion, and so far has been running wonderfully!
Finally, my chromecast is useful. Big props to Synology for making this happen.
Sorry, this is mostly just me being a fanboy for Synology since they made such an obscure device a relatively high priority and have done so better than anything else out at the moment! (no, I do not work for them).