Well, its probably slightly more complicated. From those strings, they're tying things in with the Calendar. Perhaps they are are designing a real slick, easy interface with built in items and ways to integrate it with the operating system so pop up notices appear if things go past due. Still, probably not that complicated, but when you have things like Safari and the iPod crashing randomly, along with trying to further lock down the firmware basebands to protect their profit sharing with AT&T and others, along with providing security for the new, 3rd party apps and even putting together an easy to use SDK, I doubt this is their top priority.
My theory is these are probably hooks for the SDK so someone can make their own to-do list app. I haven't programmed anything for the iPhone, but perhaps before there weren't the same hooks into the Calendar that there were for Google Maps, etc, for 3rd party programs--or at least an easy, clean way to do it.
