Lists and maps exist, but that doesn't mean they cover every country and train.
Also, GTFS is schedule data, not realtime data. When you click a train on such a service's map, it may or may not make it clear whether the shown location is based on the interpolation of some schedule data, whether the interpolation has been adjusted by some updated data (cancellations, delays), or whether it's actually based on realtime location data.
https://opendata.stackexchange.com/questions/9547/is-there-a...