Psiloc is a futurephone app that activates events and actions on your phone based on your location relative to GSM cells:
“…you can create an event to have an alarm at the moment your phone logs in (or out) a selected cell. So you will be able to sleep calmly in your train to work or school – it will wake you up precisely at your station, even if your train is late?
For places like church, theater, hospital etc. you can set a flight mode event which will just switch the phone part of your P800 off as soon as you come there! No more embarrassing rings during performance!”