While clearing my IEEE/Computer stack I read about the Universal Systems Language (December 2008 issue). Mind blowing stuff! USL and its Deal-Before-The-Fact methodology have their roots in the Apollo space program:
“We were the luckiest people in the world. There was no choice but to be pioneers. What would later become foundations for USL enabled the Apollo team to create the software for the trip to the moon.”
As is highlighted in the article “Correct use of USL eliminates the majority of errors, including all interface errors within a system modem and its derivatives”.
It is a pity that the 001 Tool Suite seems to cost $9950 :( That way we can only read (and dream) about it.
Managing organized complexity 
It’s not so bad. Take a look at their website, and how ugly it is. Consider how that translates to their experience with UI.
No fear, though. There is work being done to provide open source toolsets.
Or, you can read this book and create your own:
http://www.amazon.com/System-Design-Provably-Correct-Constructs/dp/B002G6P2FY
I do not think the USL designers care about GUIs. I was really fascinated by the IEEE article and wanted to have a hands on experience with the software, but the price is prohibitive.
Thanks for the book pointer BTW!