About a year ago we designed a system/protocol called 'SHET' (https://github.com/18sg/SHET) which consists of a central server that links many clients together. Each client can present many properties (get/set), actions (like methods, that can be called), and events (that other clients can listen for). This was implemented by me in python/twisted and makes controlling/monitoring computers around the house really easy.
About a month ago, someone wrote a system called SHETSource (https://github.com/18sg/SHETSource) which allows us to easily connect arduinos onto SHET. Since we don't all leave our computers on all the time, we have one arduino connected to the 'server' (old macbook) near the switch, which arduinos in our rooms connect to via the spare wires in the ethernet (if you only want 100Mbps, two of the wires are spare).
In my room at least, I have a pir, 3 hacked light controllers, a servo and two switches connected via SHETSource, which allows me to write all the logic in python.
Basically, we've written a hacking framework.