The audio guide by Germany-based Jourist has audio guides for some 10 cities such as Barcelona, Berlin, London, New York as well as Vienna and many more, available in English, German, French and other languages. It seems the manguage is chosen automatically by the language of your phone, which is a bit unusual. The best is downloading  free light version (it was a Venice audio guide when we tried) and and upgrade if you like. A pretty unique feature is that you can buy the access to all tours for some ten cities for only a little more than one city would cost. Download it here and or search the lite version in the app stores..