I work for a company that uses QNX, a real-time Unix-like operating system for embedded devices such as car computers, phones, medical equipment, and air traffic monitoring systems. I personally use QNX to develop QNX apps, as there's a self-hosted version of QNX for Intel that developers can download for free. It's essentially a free desktop operating system, as only the development kit is pay-for.
We work with several QNX engineers from time to time and on their last trip in they showed us a preview of the next major upgrade to the system, QNX 6.4. Like its predecessors it ran on Intel, and they said this update will take advantage of Intel's new processor architecture as well as a few new platforms. When I pressed them about it, they said they were 99% certain that QNX 6.4 would run on Apple's new Intel Macintosh.
I asked him the how and when, and he said that Apple's new Macs are going to be very PC-like, and if they can run a stock install of Windows, QNX won't have any problem supporting them either. He said Apple promised the first Intel Macs in the second half of '06, which is when QNX 6.4 would be released. He also said that QNX has at least one Developer Transition Kit that QNX 6.3 runs just fine on.
Things are looking exciting as Apple will instantly have a handful of good operating systems to run on its new Intel hardware. QNX is a good addition, and I wanted to make sure the word got out. We weren't under NDA and the QNX guys said to go ahead and tell anyone we wanted, and that an announcement was forthcoming soon anyway. So there's at least one embedded real-time Unix-like system for new Intel Macs.