I've used mobile boarding passes for international flights. I entered my email address into my reservation (or maybe it was in my JAL Mileage Bank profile? It was so long ago that I can't remember), and ever since then I get an email the day before my flight with an image attachment of a QR code that I can use as my boarding pass. The last time I traveled with my family I used mobile BPs for all of us. I screen-captured all the QR codes so I could just swipe them all one by one and scan them quickly at the jetway entrance at NRT. Kept my hands free of having to carry extra paper and was very convenient. I only get these emails when departing Japan, though. Maybe mobile boarding passes aren't accepted at overseas airports.