That's why I said I was using the Chipmunk space to represent a horizontal plane, rather than the vertical plane often used in side-scrollers. Also, the connection is that the physics engine already holds the positions for where everything is, so I wouldn't want a path-finding algorithm that created some sort of bitmap as an intermediary stage. I'm not even sure if a path-finding algorithm like that exists, but there definitely is a collision detection algorithm like that.
Here's an example of path-finding using the glaze physics engine
http://jaketastic.com/blog/heuristic-uninformed-realtime-adaptive-2d-pathfinding-using-ray-casting/I'm pretty sure similar logic will carry over into Chipmunk.
However, as I said before, I just want to see if anyone has already done this and would let me use their code before I go ahead and do it myself. I'm pretty new to path-finding, so I figured if someone had already done something it would probably be a lot better than my solution.