An unobstrusive map shows the day- and night areas of the planet. Places of international friends/family/relatives can be marked with a dot and on quick glance it is visible if "is it bright day over there?" The map can be centered on the Americas, "normal' and on Asia. The code is public on GitHub where bugs may be reported.
Originating from a 3000m long-distance relationship tis app is the result of the honeymoon trip! ;)