Nintendo has been talking up the mobile sector recently... a lot. In fact, their latest endeavors seem to center around mobile gaming. During a shareholders' meeting someone asked if perhaps Nintendo would consider making a controller for mobile devices.
Physical controllers for smart device applications are available in the market and it is possible that we may also develop something new by ourselves
This comes shortly on the heels of patents making their way into the public sphere, which reveal that Nintendo is indeed working on some sort of touchscreen device that many assume will have cross-compatibility with mobile devices or mobile apps. It's assumed that the wireless touchscreen device will be a controller of some sort for the Nintendo NX.
However, I'm not sure if the Nintendo NX is just a wireless device or a peripheral of some sort that ties its functionality into the Wii U. It's impossible to tell.
What's interesting, though, is that the patents seem to show a separate design that could very well work as a third-party peripheral for current generation smartphone devices. It features four face buttons on the right side of the panel, as well as a circular thumb pad on the left side of the panel, and a four-directional digital pad just below it.
There's no telling if the design is final, but it could very well be a controller designed to take advantage of mobile gaming, assuming that is part of Nintendo's plans when they launch the Nintendo NX next year in the spring.
According to Shinya Takahashi, Nintendo will attempt to bring more action oriented games to the mobile space and utilize the current mobile technology to create intense experiences for iOS or Android devices. For those not in the know, it's rare to find quality action games on smartphones and tablets due to their size and their reliance on very unreliable touchscreen functionality. How Nintendo would be able to pull off this feat was not discussed, but Takahashi does state that they would also be interested in bringing more general apps to the mobile gaming space, stating...
I think we will make applications, and not just action games, in consideration of what best embodies 'Nintendo-like' applications, [...] including applications for everyone from children to seniors
Takahashi also mentions that building apps and games for non-Nintendo devices has been a real challenge for the company, as they recently released Miitomo for smartphones and they have a Fire Emblem game and an Animal Crossing game in the works as well. They're also experimenting with putting Pokemon GO on mobile devices, which could prove to be interesting.
As far as controller support for mobile games on non-Nintendo systems are concerned, it doesn't look like that's happening any time soon. But with those Nintendo NX patents floating around, it's not impossible to think that Nintendo could support third-party mobile devices with peripherals sometime in the future.