I'm familiar with the Zip stove, and it's an interesting concept- basically an old-fashioned hobo stove with insulation and a battery-powered fan added.

I find the idea of carrying and monitoring batteries a bit irksome, though, and wonder how necessary that is. Seems like you might make a passive draught system work on something like the principle of hot-blast lanterns, and if that's too bulky, you could certainly use a Peltier junction to power the fan without batteries, and it would weigh less.

I have friends with pellet stoves, which are very nice and low-fuss, but they use AC for the pellet hopper feed (wormscrew) and the fan- and as such, they just don't work at all when you need them most, when the power's out. I've often thought that this would be an ideal use for Peltier junctions if they weren't so expensive. Maybe a closed-cycle low vapor-pressure turbine? There's a lot of heat coming from a stove, and it seems that no one is much thinking about the problem.