Thanks, it looks really interesting and seems to do what I just described. The thing it lacks though is - in my opinion - RPC-style messages. For example an alarm controller could subscribe to motion events, but when such an event occur it should be able to turn on sound-device immediately or shut some locks. The one-to-one communication as described here: https://github.com/mqtt/mqtt.github.io/wiki/one_to_one seems more like a hack than a proper solution.