Some people

This image is better
https://i.redd.it/cbcih51ft9cy.jpg

Oh thats great!Now it makes me wonder:Is that only for portable mode, or is there some way to connect while in home console mode?Maybe only through bluetooth?

Let me just tell you it's not confirmed to be usable for in-game voice chat (yet).
For all we know, it might be just for the DS Virtual Console service, for games that require you to blow into the mic.

this is good.

I think this is one of those occasions where Nintendo pushes something too hard in an attempt to differentiate themselves from the competition and it ends up delivering the wrong message.  It reminds me of when they kept on trying to push the Wii U gamepad and a lot of people ended up thinking it was just an add-on or with ARMS where they keep on pushing motion controls and people who don't do their research and are turned off by motion controls become unaware that traditional controls are also possible.

I'll wait for Nintendo to actually confirm this. Especially after Reggie only mentioned the app when talking about voice chat. It may work on the console, but maybe going through Bluetooth on your phone or something. Or maybe its only supported for games that use mics. Who knows. The fact that we don't have complete facts about much of the Switch with just a little over a month from release is just freaking pathetic. Nintendo truly has learned little, if anything at all.

Many people already replyed to you with different answers, but i believe the real reason the app exist is to voice chat without the need of a headset, i don t have one and the Switch doesn t have a microphone, so i can use the cell phone to talk.

sad to see ppl getting excited over this kind of news.

This doesn't confirm it, but there are some rumors floating around, and like I said before, I can see this happening