Actually, most of the time, the performance-critical computations happens in the highly optimized C modules already, so there's not /that/ much to gain. That being said, the PyPy team is working on a NumPy integration (NumPyPy).

In many cases, you can use something like python-bond to call PyPy from a regular CPython program: https://pypi.python.org/pypi/python-bond (or just use multiprocessing).