A mother with a medical condition could actually teach her 3 year old daughter to dial 911 on her Blackberry, and the little girl did it when her mom passed out one day and the dispatchers could figure out where she was! Very cool. Here's the news story.

The story doesn't mention that the daughter actually knew her address, so I'm assuming that E911 allowed the dispatcher to get the general vicinity, and then, as the story mentions, the little girl's description of the house let EMS figure out exactly which house they were in.