This is an alarm that gets triggered based on time and location. This can be easily implemented on a GPS capable cellphone.

Let's say you want to take a nap in the train, and you are sleepy and want to wake up when you are 10 miles away from your destination. Set a GPS position based alarm that will ring when the train reaches the pervious station.

Or lets say you ran out of milk at home, and you are about to go to a party. You want to stop by at a gas station on the way back, and get some milk. You can set a GPS position alarm that will ring when you pass through Schaumburg, IL after 10PM. If you don't have a GPS alarm, you can probably set a normal alarm at 10 PM, and you might still be at the party, and your alarm goes off "BUY MILK". That doesn't sound very useful