Hello, if you have checked the first steps
Write Your First Client Application | Over The Air API | Google for Developers[
^] on how to build an Android app and would like to check out cross platform development you can also consider writing a Flutter / React Native app.
However, There is no way to develop cross platform airtag projects. Here is some information related to ReactNative / Flutter:
a) React Native
you can code AirTag features in a React Native application, but it requires some additional steps and libraries. React Native itself does not have built-in support for interacting directly with AirTags, as AirTags communicate using Bluetooth Low Energy (BLE) and the Ultra-Wideband (UWB) technology.
To integrate AirTag features in a React Native app, you would typically use Native Modules: React Native allows you to write native code (Swift for iOS and Java/Kotlin for Android) and expose it to your JavaScript code.
b) Flutter
Flutter does not have airtag support either - so it would be platform specific development also in this case
Good luck on your next airtag project! =)