Windows Store Apps: Association launching

The API allows you to launch the user’s default app for a file type or protocol. Check out - UnityEngine.WSA.Launcher for more information.

You can also enable your app to be the default app for a file type or protocol. You can set this information in Player Settings (More settings are available in Package.appxmanifest->Declarations)

You can download an example project here.

You can read more here - Assocation launching.