The online railcar tracking apps (which sometimes allowed loco traces) have long been put behind username/password - since 9/11. On CR you could get a symbol from one car #.
There are many tracking apps for Amtrak and commuter rail.
There is also ATCS Monitor - although it does not show symbols. If it is available for your area, you should look into it....
I can follow a plane passing over my head with all the info on an apps on my phone ...
I read somewhere there was suppose to be a delay , but I don't see it !!!
It might be more difficult to put an app for train since there is no "transceiver" or whatever the name is .
But that would be so much more fun to take picture .