Looks like Nintendo just launched the infamous Nintendo Switch Online app for iOS and Android to get ready for Splatoon 2 which launches on July 21st. However, the app is not working right now as it is undergoing “Server Maintenance”.
I’m going to assume they’re not ready just yet and are still working on the app to ensure it will be ready on Friday, but you can download it and look at it I guess! Keep in mind you will need to have a pair of headphones plugged into your phone to communicate. You will also have access to the SplatNet 2 portal which allows you to look at stats and buy gear.