Maybe I'm the only one that didn't know about this, but there is an option for getting google maps to work when you are out of coverage. I used this for a recent sailing trip but also consider it for remote location bike trips.
You can pre-visit an area in google maps and save the location data locally on your device. Calling up google maps later when you are there --will show map details even if you have no cellphone coverage. So if you know there are uncovered areas on your route, you can preload tha maps ahead of time.