Eh... using the stove isn't so crazy. I myself was thinking along the lines of a device like a cone, an inverted funnel that could carry hot air down a tube attached to the end of the funnel. The funnel shape would concentrate the heat, so a low flame would be enough.

I didn't take the thought further, though, since high-quality vaporizers are available at reasonable prices. I'm not going to come up with something better than Da Buddha, Vapor Bros, or even Vapor Genie. However, as proof-of-concept, it's a lot of fun to make your own vaporizer (or any paraphernalia).