I wish all app designers would consider designing apps that function offline. It's infuriating to visit a web page that has been read before only to find that the browser won't show it because the network is unreachable.
Up until less than a year ago, offline web apps were not really possible. Until service workers became commonplace, the only option was AppCache, which is one of the most broken and convoluted specs ever to weasel its way into the web platform.
You should start to see more and more offline-ready web apps making an appearance as the tooling around service workers improves!
