I've got to go with BroHogan and suggest X10.
I'm going to back off my suggestion a bit! The reason is, that I am more hesitant to recommend X10 to those in 220VAC land. Prices on the 220V version seem to be 4X higher than the 115VAC versions. It's a damed shame, because the only diff is a cap and resistor. (You can modify the 115V to a 220V yourself.)
crites, the Coupler-Repeater you mentioned has really improved the reliability for my system too. It made a huge difference. My guess is that hoping across the phases is the biggest reason for unreliable comm. (AFAIK the phase thing is a N. American issue, however.)
And yes it is slow ~ 1.5 sec from signal to action, although most HA systems are mainly timed events, or triggered events, where the delay doesn't matter.
I'm not sure whether it's true or not but in reference to the wikipedia article about x10 it's totally useless in germany,
Sounds a little absolute to me! I looked at the (US) Wikipedia article about x10 and didn't get that impression, was that in the German Wikipedia?
I know that we tend to promote what we like and know, and that always makes me uncomfortable suggesting things like X10. However I'm compelled to suggest it when I hear about a $300 / 10 man-day solution that solves what might be a $40 / 1MD problem. (assuming 115VAC)
OTOH, "Your free to move about the cabin".
Almost off the soap box. Just to say, if I thought X10 was slow, unreliable, and un-cool (which it is!) I'd still buy a few pieces and see what it does. It's cheap (115V) and perhaps I'd end up using it for part of my HA system.