The idea is to have a common UI and REST API for building packages and managing repositories across packaging toolchains. Right now it supports rpm+yum and deb+apt. Packages are built in isolated Linux containers using Heroku's buildpack interface. (Would love feedback from anyone who's interested in beta testing.)
Also, have you seen the Omaha protocol?
https://code.google.com/p/omaha/wiki/ServerProtocol
It's used by a lot software, including Chrome and ChromeOS. Recently, CoreOS has built infrastructure with it and they offer a SaaS product for rolling updates. I think they're planning on using it to update Docker containers, too:
