I've written an open-source export script for Blender that extracts compound physics collision shapes authored in Blender and writes them to a YAML text file for use in a Bullet physics application.
Your C++ application will create a parent btCompoundShape and then parse the exported YAML text file to create the child shapes. The exporter supports the following shapes:
Box,
Sphere,
Cylinder,
Cone,
Capsule, and
ConvexHullHere's my blog post with more information about the exporter:
http://www.stuartdenman.com/blender-physics-shape-exporter/The python addon script is available for download on my Google Code repository (see blog post for link).
Have fun!