Garmin users probably know this functionality. It is about the possibility of assigning an attribute to any Bookmark like “Warn When Approaching”, regardless of whether it is used on the current route or not. Also in follow mode.
Usually, I had several such places that I wanted to be informed about: a dangerous place, an important intersection, nice panorama, a hidden Geocache…
Is there a place in the application and you need such functionality?
You probably mean this function?
No no. I meant the user’s own Bookmarks - as it is in Garmin, with the possibility of defining the radius of the circle activating the warnings.
However, the feature you just cited is also very cool 
It seems similar, distance / direction with alert to some map marker along the route.
The map marker’s source can be bookmark, POI, etc.
It could work in navigation where the route is used.
(follow location only knows user position)
Oh yeah, in that case it really looks the same.
Perhaps only with the difference that the warning point should be audible, and e.g. a gas station not necessarily. But this may solve the categorization of points in the future.