hok_si_la,
Presumably, you mean something very different from the many existing "test your skills" challenges such as the QOTW, Project Euler or even http://icfpcontest.org/. You walk in not knowing what the course will look like though you have a general idea based on previous episodes. Each stage is comprised of sub-tasks that must be completed before you can move on. You have a time limit. In other words, a true Ninja Warrior course.

I think this would work best at conferences - there is a YAPC::NA coming right up. You would be able to control access to external resources such as the internet. Unlike Ninja Warrior, everyone could participate simultaneously - at least at each stage. Complete an obstacle by submitting the result via some protocol and, if correct you get the next through the same protocol.

It seems like a lot of work but I would definitely sign up if someone else put forth the effort to design such a course.