Thanks to myself, timecop and Alexinparis, FreeIMU v0.4 and its MPU6050 are now supported in MultiWii. At the moment, the code doesn’t use the DMP due to the lack of documentation for it. The MPU6050 I2C master features are instead used, so the magnetometer is now read directly from the MPU6050.
Code available on MultiWii SVN: http://code.google.com/p/multiwii/source/checkout
Development discussion: http://www.multiwii.com/forum/viewtopic.php?f=8&t=1080
FreeIMU project: http://www.varesano.net/projects/hardware/FreeIMU