I have developed a small module to integrate with OpenMPI's infrastructure in a Qt way.
The source can be found here and is distributed with the MIT license.
I don't have documentation (yet), but I hope with time to add that as well as some autotests and examples, and ultimately to expand the supported functionality. For the moment it's rather simplistic and supports point-to-point and broadcast communication in an event-driven environment. It's not not really meant to be used in GUI setups because of the specifics of how OpenMPI is implemented, but it's possible to be adapted by changing the message poll interval and setting up the QtMpi entry point in a separate thread. I haven't tested it with multiple threads (yet), but should work more or less fine (it's intended to be compatible).
So for all the number-crunchers out there, enjoy!
PS: And don't hesitate to open issues, share opinions and/or contribute.