in the very unlikely event that a general purpose operating system separated me from death i suppose i would want qnx neutrino. ideally i could have someone like lockheed-martin or boeing develop an operating system specifically for whatever life enabling role much like the operating systems they use for their airplanes and air traffic control systems.
eros or coyotos might be good also but i think i would stay away from research projects.
at any rate i would completely avoid monolithic operating systems because i would hate for solar flares or cosmic rays or god knows to cause corruption on the system that results in a driver crash.