You are right, I am capable of doing an external app for this, last time I looked through the SDK it just had “Weather TODO” in it so I got discouraged on making anything of the sort, I’ll update my SDK and see if there is anything new.
If this gets a bunch of interest I’ll consider trying to slot this external app creation into my current programming TODO list, would like if people could share their GPW & GAF charts / documents they get from around the world and their ideas to guide its development.