The house monitoring project has made a little bit of progress, as I’ve now got data being collected into a rails app using backgroundrb, and can get that data back out into very pretty graphs with gruff.  (I also looked a little bit a sparklines, but that’s specifically for graphs without labels.)
 

We’re running above target temp as it’s the weekend, so the wood stove is on.  As is the furnace fan to spread the heat through the house.  I’m overloading the values for heat on an fan on to be either the bottom of the graph or a specific small value.  I need to sort out a better way to put that into the graph, which may require some hacking on gruff itself.