I'm starting to use IPython notebooks to document some of my code with interactive usage examples. In order to avoid having the documentation get too far out of date from the code, I'd like the code in the notebook to get executed on a regular basis to catch any changes in output and to flag runtime errors.
I don't know of an actual nose plugin to do it automatically, but here is a script showing the basic pieces that would be necessary for such a thing. Others have since forked it to add some functionality.
The gist is that you create the same Kernel object that the notebook uses, and run through the same execution that 'Run All' would do, and compare the resulting output. It has some primitive sanitization, which could probably largely be replaced by the right doctest functions, but it's not super complicated.