Having modbus is great and will open new doors for more NETMF markets.
Mario is using netduino but as this is “.NET”, particularly NETMF, you can use his code on any NETMF device. Code is Apache license too so enjoy.
Thanks Mario 
The library supports out of the box platforms that have built in ethernet. In order to not scare you guys away I have prepared a demo showing how it can be used on USBizi based platforms with Wiznet chip (e.g. FEZ Panda + Connect shield). You can download the souce code here:
The discussion about this can be found here:
http://cetdevelop.codeplex.com/discussions/350808
If you want to test it i recommend using application called Modbus Pool. You can use it as a Modbus client/slave to read data from your device (Modbus master/server).
Scared? Who’s scared? This looks frakin’ awesome! Pretty soon my house will be running like a well oiled manufacturing plant 
The more I think about it, the more I think CAN is an obvious choice for home automation. Does Modbus have advantages over CAN?
I come across modbus a lot when dealing with industrial automation. I never came across CAN and assosiate it with car electronic. Modbus is used in systems that are simple, in more complex BACnet/LonWorks is more common. I have no experience in home automation (besides working with XBee) but i assosiate it with KNX (former EIB) for example.
As for modbus i like it because its simple and if i were to design a device that needs to support some open communication standard i would use it.
I got carried away, I do see CAN sometimes but most of the time its used for some internal work. My company is all about integrating hardware with software platform so i look only at the 3rd party connection which is usualy done not with CAN.
Industry likes it because the infrastructure (CAT-6, RJ-45, switches etc) is almost always already available, so no cables to pull. Homes are getting there, but I think most would use CAN because of less expensive equipment and less energy use.
CAN is certainly more common in automotive applications, but it’s kinda like RS-485 with a networking stack built in for free.
If I understand it correctly, it handles noise very well, all the message checking and retransmission stuff is built into the hardware, and message filtering is as well (you only get messages you’re interested in).
Seems to me to have all the right things going for it.
Well, max packet size is 8 bytes - which is no problem for home sensors. And max speed is one megabit / second. But it does have built-in priority for messaging, so important stuff gets through first. And with FEZ it’s super simple, so it doesn’t scare you like looking at Microchips CAN code does.