UPDATE: The official english investor's meeting transcript is out:

https://www.nintendo.co.jp/ir/en/library/events/160203/04.html

https://www.nintendo.co.jp/ir/en/library/events/160203/05.html

https://www.nintendo.co.jp/ir/en/library/events/160203/06.html

tl;dr

My Nintendo – features detailed, launch plans

Miitomo – breakdown of the app, “Miifoto” feature, launch plans

Mobile app payments & wanting 100 million My Nintendo members

Nintendo outlines launch plans for first mobile app Miitomo and My Nintendo

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Lots of news during Nintendo’s financial results briefing from Tatsumi Kimishima, but apparently no one here in VGC has posted news updates on these services.

The My Nintendo point program will begin in March in 39 countries. There will be Platinum Points like the prior Club Nintendo and Gold Points for coupons. My Nintendo is starting with a points program, coupon, emails, and web downloads. It’ll expand to friends list, cloud data, and in-store. Kimishima also reiterated that the first goal is to quickly have 100 million people registered with My Nintendo.

Source

The early word out of today’s event is that Miitomo will launch in mid-March in Japan. This will be followed abroad during the same month on iOS and Android. Miitomo pre-registration begins on February 17, with plans to launch next month in 16 countries and 8 languages. The latter includes English, French, Italian, German, Spanish, Japanese, Dutch, and Russian.

Source

Because is not mentioned at all new account system, I assuming that new account system is basically integrated in My Nintendo, actually My Nintendo is new Nintendo account system!?

We'll get better translated info when the english investor's meeting transcript comes out.

Here are some more updates from NintendoLife. 

As many of you are likely aware, Nintendo recently held another investor's meeting. While these things aren't strictly about big announcements that are entirely relevant to the general public, new details related to the company's near future are often divulged in one way or another. It appears that the latest meeting didn't carry any major new announcements, though we have a clearer picture of what My Nintendo will entail.

The transcripts from the briefing are still in Japanese at the time of writing, so bear with us, as we're going off of unofficial translations at the moment. For starters, My Nintendo will go live in March in 39 different countries. It seems that there will be two points systems at play; Platinum Points will essentially function like the former Club Nintendo, with goods and games being up for grabs, and Gold Points will act as coupons for the eShop. My Nintendo will initially start with emails, points, coupons, and remote downloads, then will later expand to encompass the friends list, cloud data, and in-store credit. Additionally, you'll be able to redownload digital games from the eShop onto other devices.

Source

As you can see in the image above, Miitomo will have a Photo Mode that's somewhat reminiscent of the AR cards used with the 3DS; there's no card in this instance, naturally, but it'll allow users to create and share real-world images that feature their Mii.

It was also reiterated that Miitomo is on track to launch alongside the My Nintendo service - it'll land in Japan in mid-March and in another 15 countries at some point that month (more will follow); a map of applicable countries is above, including North America and much of Europe. Pre-registration on iOS and Android will begin in 17th February (date to be confirmed for other countries) to enable users to download it right away once available; notably doing this will entitle those users to a Platinum point in the My Nintendo service, so it's the first incentive for the loyalty programme, too.

With this app Nintendo's goal is to rapidly gain users through the free-to-play aspect, and hopes for cross-pollination between Miitomo and the new account loyalty service. The first goal for My Nintendo membership is 100 million users, showing how the programme will target those that don't necessarily own Nintendo gaming hardware at the point they initially register.

Source

I don't get it. How come they can't release Miitomo worldwide. It's a mobile game for god's sake.

I assumed they weren't done with the localization for a lot of those countrys. They are launching it in their core markets simultaniously though.

I dont think its not releasing in the other countries, its just that most likely you cant receive the goods or physical bonus from the My Nintendo program, or something along those lines.It still sucks though

Edit:And also language translation problems.Though it dosent make sense in some countries, such as Brazil not getting support, since Portugal share the same language and its getting the app.Mostly comes down with the cost x profit of implementing the program in the country

I know Brazil isn't highlighted on the map for MiiTomo, but I read in some other article that it was supported at launch for Nintendo account. So who knows, maybe this is a mistake and MiiTomo is launching in Brazil toghether with Nintendo account, like everywhere else. Other than that, i got nothing.

cool so this means we get achievements soon?

Will Miitomo be avalible on 3DS and WiiU? I know it's a mobile app, but there is no reason not to offer the service on regular consoles.

I don't think Portugal is getting Miitomo but they will get the new Nintendo acount and so will Brazil