Yay, finally, there is a supported API for the Calendar. It's always been such a strange omission and has really hurt the emergence of quality calendar apps and third party calendar integration. I've personally omitted otherwise handy features from apps ("Add this to my calendar") because the calendar APIs were missing and I really didn't want to go the unsupported route.
Correlation is not causation, but if the Android team knew Siri was a threat early on, they were smart to make the Text-to-speech APIs public.