Interesting. I wouldn;t discount it but, speaking only about heating an avg size room for hours, I'd either have to try it or see if you or someone else does and reports back. My suspicion is it might take the chill out of the room if the outside temperature were just a little chilly, but on a cold, cold night? hmmmmm better than nothing at all.

We heat our home with nothing but a woodburning stove....a nice one, I'll grant. but still just a fanless woodburner. So, without a lot of detail, I'd be highly suspect of the claim that a 2 gal bucket of rocks would do more than take the chill off, and then only as long as you were sitting right by it. This is not to undermine the general idea of bringing the heat in though.