Another reason to save, working iPhones. They also make a fine iPod.My BMW Connected App on my old iPhone 7 works great, even if I loose cell tower coverage.
The maps are downloaded to the internal hard drive on the iPhone.
I run both the BMW/Garmin Navigator 6 (2nd Generation) and the BMW Connected App. And in the hilly mountains and valleys of NC, SW-VA and WV I have no problem having the BMW Connected stay connected and on the planned the route. Sometimes the Nav 6 GPS looses its satellite signal and starts wandering of the route by some distance, before it finds another signal, while the old iPhone 7 stays connected to whatever signal it uses and continues showing the route on the actual road.

OM