Schiphol already has a decent app for tracking flights and finding gates, luggage, and shopping, but I don't see how this will dissuade the providers of those other apps.
Also, this issue is not limited to airports - there's lots and lots of integration to be done.
Say, if I want to take a bus in Bergen (Norway's #2 town, or, if you ask the locals, #1) - you need one app to find out which bus(es) to take, then another to buy a ticket. If you want to buy a ticket for the airport coach? Oh, you'll need another app for that. Actually, you'll need two, as there are two coach companies.
And, getting to Oslo, (#1, or, if you ask the people in Bergen - #2) you'll need another app if you want to take the shuttle train into town, then yet another for getting tickets once you transit to trams/buses in the city centre.
&c. If public transport companies could agree on a way of sharing payments, the market is more than ripe for unified apps for route planning and ticketing, at least on a national level. (Expecting standardization to cross borders is probably a bit of a stretch - and, unless you happen to live in, say, Liechtenstein with half a dozen countries within walking distance (yes, I exaggerate), not much of a concern, really.
(You can actually use the ticket vending machine by the bus stop near my house to buy a ticket which can be used to go by bus from my house to Zürich station, then by express train from there to a station in the mountains, and then by bus up to a ski resort car park, and then by cable car from there to the resort proper, and then by chairlift from there to the top of the mountain, and then it's your ski pass for a day's skiing, and then it takes you home again. One ticket.)
I started writing out the list of steps I go through to visit a new city effectively, but it's much too depressing. There's a huge amount of local knowledge that IMO shouldn't be required just to visit a city as an outsider without getting ripped off.
[1] https://productforums.google.com/forum/#!topic/maps/aPWIrf6H...