I'm not a protocol designer. I'm sure that people have been thinking about this for a long time, but I bet all the thought has been behind closed doors and not in a public appliance design forum and framework. That said, my vision is of a household full of devices that
> * speak to each other over TCP (Transmission Control Protocol)/IP (Internet Protocol)
* are explicitly tr ansport-layer [1] agnostic, so any TCP/IP transport works, whether it's Powerline Ethernet, Wifi Ethernet, Bluetooth, GSM (Global System for Mobile Communications), Lonworks [2] or tachyon telepathy
* use a Zeroconf [3] address assignment and service discovery
In the most basic implementation, for example, a Powerline time broadcast system allows every device to be time synchronized, so you don't have to reset all the clocks after a power outage. More sophisticated systems can advertise themselves as displays, inputs or outputs. To use the tired coffee maker example: your coffee maker thus no longer has to include its own scheduling device; your alarm clock can schedule all necessary tasks, find your coffee maker as an output device with a standard set of services, and just tell it when to start percolating at the same time that it tells your Wifi rabbit to start caching its the news and traffic MP3s. Your pressure-sensitive carpet can just broadcast “turn on 1/10 power” to all lights in its vicinity, which turn on as you walk to the bathroom in the middle of the night, they light your way. If you have no such lights, they don't light.
“Why we need a good appliance communication protocol [4]”
Any sufficiently advanced technology is indistinguishable from magic.
“[Arthur C.] Clarke's Third Law”
The link wasn't directly from Blahsploitation [5], but he's also thinking along similar lines here. And while I would love the lights to turn on as I walk about the house, or the tea kettle to turn on ten minutes before the alarm goes off, I worry about making this seem more magical than it appears [6].
[1] http://en.wikipedia.org/wiki/OSI_model#Layer_4:_Transport_Layer
[2] http://en.wikipedia.org/wiki/LonWorks
[4] http://www.orangecone.com/archives/2007/01/we_need_an_appl.html
[5] http://blahsploitation.blogspot.com/2007/02/kind-of-like-i-was-assuming