Have you ever stayed after work in London for a few drinks and ended up falling asleep on the train and missing your stop? My husband has a couple of times in the last 6 months and ended up at the end of the line in Bedford, resulting in a very expensive taxi ride home at 4am.
I haven’t tried this app myself yet, but I absolutely love the idea of it. GPS Alarm (free from iTunes) lets you set an alarm based on your location and will go off when you get close. The only other solution is to stick a post it note on your forehead with your stop written on it, like this slightly inebriated woman did!