This sounds like a solution to a problem that doesn't exist in reality. You basically only ever actually need navigation when driving/riding in a foreign city

This sounds like a solution to a problem that doesn't exist in reality. You basically only ever actually need navigation when driving/riding in a foreign city that you don't know yet. If you're on a cycle, using headphones to receive audible instructions should suffice (unless you spend most of your days riding foreign cities). If you know the city instead, you generally know its quirks better than any navigator. If you're travelling on highways you can just take a look at the map on your phone and preplan the few next turns in advance. When on a cycle, it's easy to just pull over and check where you are and whether that little road will take you in and out of some location.