DoBy looks very interesting, basically, it will raise exception when the current time has passed the specified time, for example:

>>> from doby import TODO
>>> from datetime import datetime, timedelta
>>> delta = timedelta(seconds=1)
>>> now = datetime.now()
>>> TODO('I need to come back to this', now + 60 * delta)
>>> TODO('I need to come back to this', now - delta)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "doby/__init__.py", line 38, in TODO
    DoBy(note, doby)
  File "doby/__init__.py", line 28, in __init__
    raise self
doby.DoBy: TODO: I need to come back to this
>>> TODO('I need to come back to this', now)
Traceback (most recent call last):
    ...
doby.DoBy: TODO: I need to come back to this
>>> TODO('I need to come back to this', '17-05-2013')
Traceback (most recent call last):
    ...
doby.DoBy: TODO: I need to come back to this

Interesting as I said, but it might not be reliable due to the nature of the code. Think about coverage.py, got what I am thinking about it? The raised exception might come too late or never come.

Still, this is a unique conception to implement a notifiable TODO.

DoBy is written by Adam Drakeford under the MIT License, currently version 1.0.2 (2014-05-17), for both Python 2 and 3.