This morning I finally finished the hip constraint! You can now download it here. Just like the shoulder constraint, it comes with MEL scripts designed to assist in setup.
Speaking of the shoulder constraint, I found some pretty egregious math errors in my shoulder constraint node, so I have uploaded another update to it. Not only does it actually work as intended now, the math is greatly simplified and more closely resembles what you need to do to port it into game code.
Enjoy, and please let me know if you have any problems while using it!