I looked at the app.
It appears to be a tool similar to the Visit Japan Web which collects in advance the traveler's trip information to help reduce the time at the actual process at the arrival airport. Visit Japan Web collects information such as flight number, hotel, duration of stay, answers to customs' questions... Then upon landing in Japan, you will still go through the immigration process for fingerprint collection/photo taking and the customs process.

Just my initial guess without actually using this app.
Looks like it is rolled out for use in Sweden only at this time.