I found this script a few weeks ago while I was trying to do the same thing [
www.crai.archi.fr] (search for "su2stl.rb"). It seems like a super simple, free script that does the same thing. Unfortunately, it has no options to optimize the resolution (# of triangles) in the resultant mesh - if it's too low quality for a particular application you're out of luck. Still, I can't imagine it would be that hard to add that functionality in (disclaimer: I haven't looked at the code).
