[MNBlockHead]

Regarding potential wifi issues at conventions and game stores. I find access to convenient places to charge devices to be a much bigger issue. Whether online or off, I ALWAYS bring printouts, just in case.

If no wifi, I have my cell data plan and mobile hotspot functionality.
If no wifi AND no cell network, I have HLC
I carry a backup brick that I've used to charge three iPads and two iPhone with heavy use on US to Taiwan trips, but if it runs out of juice or stops working, or my computer does, then I have paper.

As long as you can PRINT your character sheets, I don't care if it's always online. In my experience power issues or software/hardware failures are a bigger concern.

So while I am a bit dismissive of the issue, still, I *DO* think that there should be a way to make it work offline. I know DnD Beyond is working on offline access and they are 100% browser based. I'm not sure if they are going to develop an app that will cache content to the mobile device or use the technology available in some browser that allows you to work in the web app offline, similar to some Google Apps products.