Rewards will be separated into two different tiers: Gold Points (received from buying Nintendo games, consoles and digital content), and Platinum points that you'll get from logging into your "My Nintendo" account, playing games on your phone, and other non-transaction based things.
How you earn the points differs, as does how you use them. Platinum points can be exchanged for digital contents (wallpapers, game DLC), while gold points will change into discount vouchers — for buying more Nintendo stuff. Wait, no more Mario caps and frivolous Nintendo toys, a la Club Nintendo? Not quite: Nintendo's investor briefing slides add that you will be able to swap Platinum points for "original goods", mentioned separately to digital swag.
The "My Nintendo" service will launch in full in 16 countries when it starts mid-March, coinciding with the release of Miitomo, the company's first smartphone title, what it's calling an "entertainment app" — and not a game. I think Nintendo's splitting hairs, because Miitomo still looks very similar to the 3DS' Tomodachi Life title, with your own avatar living alongside other similarly-made Miis — presumably your real-life friends.
The app will come to both iOS and Android next month, and it'll be the first of at least five smart device launches that Nintendo will make between now and March 2017. To make the most of its smartphone home, a feature called Mii Photo will allow you to blend together your Mii character with photos and captions, ensuring Nintendo's first smartphone gambit is easily shared on social networks — outside of just the app itself. Until then, you can show your support for all things Nintendo on your phone with this (Japanese only) Mario Maker Wallpaper... Maker.