setBreakingImpulseThreshold(btScalar)
This is perfect for the kind of fracturing I want the player to experience in kyuplex.  Although learning about Voronoi fracturing gave me a hard on, it's too complex and doesn't mesh with the cubic visual theme.  Remember the kyuplex philosophy throughout.  
   To start, the player cube will consist of four smaller cubes tied together with btPoint2PointConstraints.  This simple constraint does the job perfectly, keeping the playerCube together until an impact of sufficient force (BreakingImpulseThreshold) breaks it apart; aka death.  This structure even makes it possible to clip an edge and lose an outer cube, but if the majority of cubes are still intact, you can continue with your damaged cube.  
As the game progresses, the structure of the playerCube will become more complex, with an outer shell, or 'shield', of cubes with stronger links and more mass, that must be broken away to reveal the inner, more fragile 'heart' cube, that holds the players survival : ) Spoiler.
Plus, determining the status of broken links is easy through btTypedConstraint->isEnabled()