I created a couple of location based alerts just to try out this new feature in IOS5. I set up an alert to trigger when I had dropped my kid at school and the other one when I have arrived at work Well the first alarm when off while I was still 6 or 7 blocks away from the school. yesterday I set it to alert me when leaving work but it did not go off until I was a good block away from the building. However this morning was right on, it rang as I was parking in front of our building. Does it work with actual gps coordinates or with the street address information provided by google maps?