Passing data between native and web based apps

I have a web application based on Angular that will run within a phones basic web browser.

This app also will have a companion app that will be delegated some tasks such as barcode scanning etc!

I need the two apps to chat to each other, I know I can possibly use deeplinks to launch the companion app from the web app and also can use web sockets (with the help of a cloud service) to get information from the companion app back into the web app.

But, I also need all of the above to work while the mobile device is offline

The companion app will likely be built within a ionic, cordova or Xamarin platform!

Any thoughts, suggestions or ideas from the crowd?