Sweenie's in the process of writing a Blitz wrapper for the Tokamak physics engine at the moment, and it sounds like its pretty close to done. Tokamak includes a variety of collision zone shapes which can be combined to fit over a mesh fairly tightly, or at least I got that impression from the info at their site.
Check out this post for more info.
http://www.blitzbasic.com/Community/posts.php?topic=29381
Check out this post for more info.
http://www.blitzbasic.com/Community/posts.php?topic=29381