If I were to make an appliance/device/meter/controller today, I would make it speak Modbus. You will note I have not defined my domain, market, breadth, nor whether wireless is needed, nor whether it is a consumer or end user application or for the enterprise.
The Modbus assertion is the aggregation of the nuances across the board… all the way from the level of hacking together a small Arduino http://en.wikipedia.org/wiki/Arduino based controller for sensing the kitchen window open - through medium sized embedded Ethernet controllers based on something like Lantronix Xports http://www.lantronix.com/device-networking/embedded-device-servers/xport.html - to the level of large equipment controlling real world industrial and mechanical processes for large enterprises (like entire agencies of sovereign entities).
Note that I have not specified Modbus over RS485 or RS232 or TCP/IP; nor have I specified layered ways of transporting the protocol (like Ethernet, Wireless and Fiber).
One can poke at Modbus saying – no security, no object model, and little structure. Modbus’ beauty is in its simplicity, and in that one's needed features can be overlaid. Two of my favorite overlays are BACnet and XML, but even these can be said to incompletely address concerns about security and standardized device model representations. But again, one can overlay, and for those who do not even understand what a “standard device model representation” might get them, they can have Modbus now, and deal with that issue later, once their understanding deepens.
Dealing with Modbus “now” is what it is all about. One way or another, with a public Modbus profile of implemented functions, and register map, for a device, one can get connected and talk to it. Systematic functional understanding can be overlaid as one learns.
Some have taken up the Modbus banner. Temco controls has done so in fine fashion http://www.temcocontrols.com/ .
Most meters have Modbus interfaces. Here are a few (in no particular order and without effort to be complete):
http://www.electroind.com/shark.html
http://www.eaton.com/meters
http://www.powerlogic.com/productcategory.cfm/c_id/1
Appliances that consume electric/gas/water (washer/dryer) and all things renewable (solar, inverters, wind, nano-hydro) should take up this banner. Appliances do not appear to be going towards HANs fast in any case. But the Sunspec Alliance http://www.sunspec.org/ is notable for placing at least some basis on Modbus (as well as more forward looking XML).
See my recent article in the December issue of Automated Buildings on making a small BACnet device where Modbus as a stepping stone is alluded to http://www.automatedbuildings.com/news/dec12/articles/cimetrics/121122110404cimetrics.html .
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In manufacturing, SCADA is used to make sure that productivity targets are met and all systems run smoothly. The SCADA system on a production line tracks how many units have been produced and how many are in various other stages. Analog values like temp at various production stages are also measured. Imagine how important it is to know the temp of molten metal that must be formed into usable products.
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