How fast a train can go?

This morning I had to wake up at 4 am because I had to go to the airport because my girlfriend was going back to Turin. While on the gatwick express to London Victoria I fell asleep because I was bloody tired. When I woke up everybody around me where standing because the train arrived at the station. Suddenly I started thinking about something useful for that scenario.
Imagine how many people in the morning took the train to go to work. For sure lots of them would love to sleep a bit on the route especially if they are far enough. At the end, almost every devices could understand what's about their right position. The range could be a bit wide or really small. Google maps knows the right position of a station. So, the equation is really simple: when the user drive directly into the interested station range the device starts ringing. The main problem is the battery saving factor. The app should consider the train average speed (I think it could be calculated to be not too much neither too poor) and estimate the time between point A and point B and start requesting data every X minutes. Simple indeed but really effective.