The currentcost meters are fairly cheap, OSX-capable I think, and very popular in Europe so there are lots of little scripts for them. In the us you can find them at http://currentcost.net/buynowmain.html

The DIY rig at http://openenegymonitor.org/ is fairly straightforward, even if you're not that technically inclined....

Otherwise I'd just echo the suggestion to suck it up for the extra $50 and get the Ted 5000

My recent time-waster is finding a way to make all these different gadgets able to talk to all the various websites ...