Best app (or website) to check real time changes/delays/transfers?

Austria ÖBB Scotty App or fahrplan.oebb.at 

Switzerland: SBB App, sbb.ch

France: sncf app? or the name is now sncf-connect.fr but it is terrible.

I would always use the planner of the country you are traveling in.

In line with what @Angelo already said, I also recommend DB BAHN's scheduler.

I indeed have DB Bahn and I like the use of it, is it is good/reliable enough for all countries?

thanks

Current delays are a specific thing that by far not all sites will have available. Bahn.de is best for general advance info, and as above, it should be pretty self-evident that the site of the local railway is best for that day-if you visit more countries you can gain some knowledge as to how much these differ!