Hi Mark,
Welcome to the Tobii Developer Zone! Cool to see that our technology is attracting professionals within so many different areas. We have done some pre-studies within CAD, but right now the focus is mostly on gaming. Therefore, a UDK integration would be very nice as you say. Since the complete C++ source code of UE4 is available, it is possible to make a really good integration. If you want to do a pre-study on UDK you are very welcome to share your results with the community. We at Tobii also want to start exploring UE4 possibilities, but there is no time for that right now.
-Robert