The only sites that I know of in this sort of category are
http://www.hz-mapper.info/ for Croatia which is really only intended as a "bashing" aid for the big GM diesels. On
http://www.hz-mapper.net/ (also Croatia) you can look up a given loco / coach or even wagon
hock: and it will tell you what train it is on but (as far as I can see) not exactly what the train is or how it is running.
For Hungary you have
http://iemig.mav-trakcio.hu/3.0/ which will show you on a map exactly where a train is; if you hover the mouse over each "train" it will tell you which loco is working it and the train number. Beware that this does not work for anything other than MÁV locos and units at present, GySEV, ÖBB, ZSSK and private operators do not show up.
One thing to point out is that if you want to access these sites on the move, beware of data roaming charges on a mobile phone / tablet as they can rapidly mount up. Certain trains in Hungary are fitted with Wi-Fi and I believe that some stations are, Sopron certainly is - I managed to check in for a flight whilst there but, sadly, it wasn't much use in helping me find the GySEV class V43 locos I was after.
