Now I'm in love with Progressive Web Applications. You can install app just by visiting URL. It keeps all its data local. It works offline. It can send notifications. It is fullscreen. It's... awsome.
My second love is Web Sockets. Once I've got the task to create app for event. Guests by using their mobile devices could ask questions, view the presentation sync to the projector, chat and use some other features. We've done this app. It was very impressive when 600 mobile devices in the hall changed the slides of the presentation following the lecor. Simultaneously.
If you need any of my skills, I'll be glad to help you )