If I were installing some home automation, and I could secure it properly, I would put internet-enabled sensors and controllers all over my house and get an app for my phone to control and monitor it. I'd want to get alerts when my doors and windows are open if I'm out of the house, and just a basic report on those states available at all times. I'd really like to be able to close the doors and windows remotely, in case I left them open and I hear there's rain coming. That also goes for the garage door: alerts when it's open, remote control to open or close it.
I'd want to be able to switch the lights on and off in blocks all at once, and be able to check and switch off appliances and power points too, in case I think I left the oven or iron on. It would be nice, but not essential, to be able to control my TV, DVD and media centre from my phone, but that can be a separate project.
Mokalus of Borg
PS - In a pinch, I would probably settle for an "all lights out" switch in the bedroom.
PPS - I think home automation would be cool, but then I struggle to think what I'd actually do with it.