Like Guy says, it's been done a few ways. That yurt build he is describing is pretty cool. It's here....
http://www.flickr.com/photos/fishermans ... 133608314/However, I totally understand what you are describing. I have thought about it often, and folks who sit on my outside system seem to come up with that idea a lot. My outside system, the one in the half barrel video, had a bench that was a dead end. The hot gasses from the system worked their way out through it through a passive effect that's referred to as a "bell" in masonry stoves. I thought that would be neat as well, just have a dead end bench from an outdoor system go inside a house to provide warm seating or sleeping areas. Upon further reflection, to me it really only makes sense for a small guest cabin or something, where heat was only desired occasionally. If you were trying to heat a place that way you would waste a lot of heat by having the barrel outside, and it would be a pain to always go out there to keep it going.
I still think it's a great idea, especially for summer guests. Well, here anyway. Summer nights are cool, and after sitting around a fire outside it would be really neat to go inside and sleep on a warm bed/bench. Going outside in the winter to try to heat up your inside though, not so much. That's my take on it, but I still think it's a cool idea.