Here's some real rickidy idea I just came up with. about making a vaporizer using a piezo electric lighter as a heat source.
The casing would have to be WELL insulated, and it would need a ventilation system so the lighter could light.
The fan would rotate on it's own by the heat in theory.
There would be no fuel residue on the product and if you were skilled enough you could get your product to vaporize. But it'd definetly take some skill.
One major flaw with the design I can see if that if the lighter didn't light you'd have NO idea, until you realized the thermometer wasn't going up.
Now I don't know if this would work at all but it's an idea.