A friend actually picked up the "odometer" for me, so it was free. But it was about $3-$4. Surplus. You get what you pay for. I think most of them in the pile ran off of 240VAC or something wacky that's used on airplanes, but this one (supposedly) ran at 120VAC. Used to work pretty regularly, but not so much anymore...
I simply wired a lamp cord to it & plugged it into my power strip along w/ my marquee light, monitor, etc., so it's supposed to simply log how long my machine's been turned on.
-Jason