One thing I'll say for Siri: a few months ago I had an idea for a dictaphone device with a calendar function and voice recognition. As we know voice recognition is notoriously unreliable, but I figured it could be heavily optimized for the lingual subset necessary for setting appointments/reminders. I think that would be extremely useful to people with bad memories (eg. many elderly people), or lots to keep track of. Everyone I mentioned this to thought it was a great idea.

Looks like Siri does precisely that.