This will demonstate the use of service workers with Rails. To keep it simple the offline experience will be to display the nearest, upcoming 3 events that are being attended.
Try out Yelp Event Assistant. Note: Yelp Events is in beta so some zip codes will have no events; use zip codes for major cities for best results. Chrome Dev Tools has a way to simulate offline. Click on the Application tab, and then Service Workers, and then check Offline. This will simulate no network for that tab.