Can the app be used without internet / SIM card? What's the expected data usage?

The Kurviger App can be used without internet or SIM card, but there are some limitations.

View the map:Yes
If you have downloaded the appropriate offline maps.

Navigate/Follow the route:Yes
Kurviger is very resilient when leaving and entering the route again. We also provide helpful tools to get back on route.

Import a route:Depends
The Kurviger app can import .kurviger files without internet and allows full featured navigation on that route. For other route files like .gpx, the Kurviger app can show the overlay without internet, if you want to fully navigate along a .gpx, this can be possible without an internet connection. You can find more information on this in Offline Routing Guide.

Calculate a route:Depends
Calculating a route can work without an internet connection, offline routing has different properties than online routing. You can find more information on this in Offline Routing Guide.

Search for an address (geocoding):No
Searching for an address requires an internet connection. You can select locations on the map without internet.

Hillshading:No
Hillshading requires an internet connection and is not included in the offline maps. Compared to the routing, hillshading requires quite a bit of data, so if you have a small or expensive data plan, we highly recommend to disable hillshading.

This depends on the length route and the area of the route. To give you a rough estimate, with 1MB (note: 1GB are 1024MB), you can calculate more than 100 routes, each 100km long. So the data usage is only minimal. During the navigation no data is required for the routing.