Hi Patrick
I'm into electronics, although many years ago I actually did anything more complex it still sticks. :-).
Depending on your coffee machine it should not be to hard to do it.
I have one of those 1 button automatic espresso machine that grinds the beans and stuff, but it takes only a minute to make a cup of coffee so not really needed.
But if you have one of those brewing kind of machines, then I suppose if you prepare it with water, filter and coffee, then a simple wall plug type switch would do.
I read into Xbee, and from what I found was that although it is using the same frequency as Zigbee, they are not compatible, as they use a different stack. So it will not be possible to use the built in Zigbee in Almond+ to interact with Xbee directly.
But if I succeed with my idea, then it it should be possible to use the Arduino as a gateway to the Xbee network.
I had not thought of the built in serial console, not sure if would be possible to use it, but I might look into that. Maybe you guys know if it has a /dev entry on the router?
My thought was to use a USB-Serial such as the one that came with the Dev units, I also have an Ethernet shield, but I have not come as far as learning to use it. ;-) Still only on 6th project in the book. And I don't even think the book covers the ethernet shield.