How is Internet access available at the start and then not available in just walking distance? Eh, it doesn’t matter. Internet access is not necessary once the app is downloaded. GPS should work without Internet access.
Then, the Hype project would be exported to HTML and then those exported files would be added to a WebView. Basically, you’re making an app with web content.
Leaflet.js could be used to keep the coordinates straight. That’s an easy way to integrate an artwork layer. Yet, if you have your own maps, it might be easier to skip that, You’d just need to know the latitude / longitude bounds of your map. If you don’t have a map, then visiting OpenStreetMaps might be helpful.
Anyway, that’s just theoretical. While I have expertise in this area, I haven’t used Hype to do it.