Got back on track with the arduino yesterday. Using this library I found1 on github.com2 I now have an app on my phone that I can use to check the state of two lights, and then turn them on and off. On my phone! OK, they are just LEDs rather than wall lights, but the principle is the same. Also this is making use of a server that I've written that needs to be running on the home network (I used my macbook in this instance) but this is a temporary step - I can do it direct on the arduino itself if I buy an ethernet shield, but I wanted to get started without having to buy extra hardware first. Next to get the arduino connected up to real light switches, and some thermometers and things and my robot house plan takes another step forward.
I can't show you my home webpage yet, it's too poor, but I will share (an example) when it's ready.
arduino: Microcontroller, hardware prototyping platform, a tiny specialised computer.