After watching Guido's Google IO talk and hearing the mention that it can be extended (thus providing an instrumentation mechanism for recording your own events) I am still at a loss on how this would be done.
The functions are all for handling RPC and not simply start/stop calls an expensive function (or wrapper) can make.
Has anyone extended the library, more to the point in a safe manner that doesn't require overriding the original?
I was referring to the ability to record custom events. A simple example is:
from google.appengine.ext.appstats import recording
recording.recorder.record_custom_event('hello', 'data')
Note that you should really check whether recorder is not None before calling its record_custom_event() method.