There is a rather detailed article on ZigBee in the current issue of Dr. Dobb's Journal. It's a big download because of the screwy way DDJ distributes their magazine content online, the entire mag as a PDF file. The digital home technology is a hot area for investment, and more important to homeowners, offers real alternatives to the way their manage their homes.
I have 2 examples that I'll share, the first is the new irrigation system for our landscaping we had installed this summer that uses wireless moisture sensors throughout our property to activate the sprinkler systems only when the ground is dry. It's saved us a lot of money on water ($$ in California) and more importantly, enables us to conserve water while still enjoying the landscaping of our preference.
The second example is from just a week ago; the weather started to get a little chilly at night so our home heating system has been kicking in. Unfortunately, the thermostat is located in the worst possible place, in the room that gets the most sun and has a fireplace so it really cooks up nice and toasty at night until we go to bed, and then the residual heat in the room keeps it warm most of the night. The net effect is that the rest of the house is frickin cold. My wife told me she wants to get a space heater for our baby's room, to which I said NFW because those things are 1,500 watts (that's 12 1/2 amps) and "what am I, the *@^^damned utility company!". This, my friends, was a big mistake on my part... putting economic concerns ahead of the baby's welfare (let's just say the baby's room isn't the only thing chilly around my house at the moment).
The problem with the thermostat is that it's hardwired to the actual blower unit and furnace itself, so relocating the thermostat is a big deal because you have to fish new wiring though the walls to whatever the new location is. So I'd have to have an electrician come out, and then out again because they would screw it up, and then back out again because they would end up breaking something completely different. Not only would I end up with a big bill from the electrician, my kids room would still be cold, I'd have the space heater in there dimming the lights for the entire neighborhood, and my wife would still be mad at me.
Technology has come to the rescue. I figured "hey, there's got to be some kind of wireless sensor that won't require a lof of time and work to install" and sure enough, Google revealed there are more than just a couple. I bought and installed a thermostat that has 2 wireless remote sensors that can be permanently mounted in other rooms or just moved around to wherever you want. The remotes operate on the 418mhz band, meaning they have good range and don't consume a lot of power, the batteries should easily go through the entire winter before needing replacement. We now heat our home according to what the coldest room in the house is, a great improvement over the original system, and all for $300.
The next step would be to replace the floor registers with mechanized units that can be opened or closed based on the room temperature to ensure a consistent temperature throughout the house. This is probably not in the immediate future because these units would require a power source to operate the aperature, plus more sensors.
Why am I telling this long story in relation to an article I read on ZigBee? Because ZigBee could end up being the most important nearband wireless network technology in the years to come. Designed as a low power consumption and low cost technology, it's also capable of handling really large sensor networks, up to 65,000 nodes, as well as having high security built in from the onset to prevent tampering with or eavesdropping on the networks by intruders.
The power consumption feature in the specification is a really important part of the technology. A ZigBee device will sleep more than it's active, this is call a "low duty cycle", and with the active power at 10mW and the sleep power at 10uW, a AAA battery will power a ZigBee device for 37,000 hours on a duty cycle of .1 percent. What all this means is that wireless light and appliance switches, security systems, environmental control, and much much more... and that's just in the home, I can't even begin to imagine the full scope of industrial applications. Imagine all the wall-mounted switches in your house not having to be wired to the whatever they control, the cost savings are significant.
The bill of materials (BOM) for the devices is also light, translating into a low cost of production. Requiring no more than an 8 bit microprocessor with onboard RAM, the 802.15.4 radio, and a battery, ZigBee devices can be manufactured and deployed inexpensively with the extra cost for the device more than offset by the reduction in wiring alone, not to mention the increased capabilities. Try to match that with Wifi or Bluetooth... you can't.
ZigBee is no one-size-fits-all technology, in fact, the low data rate topping out at 250kbs and limited range make it inappropriate for most applications. For digital home and industrial applications the niche technology may be the perfect fit, combining low cost with efficient and troublefree operation. Look to hear more about ZigBee as the standard approaches final approval. The ZigBee Alliance is a great source of information