Kotlin Multiplatform Mobile is a solution to write once for Android and iOS apps, using Kotlin.
Kotlin Multiplatform Mobile is an SDK that allows developers to use the same business logic code in both iOS and Android applications. KMM now goes Alpha, and you can start sharing business logic in your mobile apps with it right away. It includes the new KMM Plugin for Android Studio, which allows you to write, run, test, and debug shared code in the same IDE.
The new Kotlin Multiplatform Mobile developer portal is up, have all you need to know to create cross-platform apps.