A developer that goes by the name of winocm has published his port of XNU for the arm architecture on his github page (
https://github.com/winocm/xnu). This port supports the ARMv6 and v7 architecture, and provides basic support for the Beagle and ARMPBA8 boards. He has also provided a minimal skeleton for RaspberryPi board support (/pexpert/arm/pe_raspberrypi.c). Currently this project can still be considered to be in it's alpha stage, as there are still several bugs to be fixed and functions to be implemented - but the kernel does apparently boot.
I can't wait to see what comes out of this!
