Imagine you are working with remote team all around the globe and want to schedule reminders based on others location.
With this app, you would add cities that interest you as a proxy for specific timezones. Added reminders would be tied to selected cities and the reminder time would also be in the timezone of the city.
For example you wan’t to remind something to your colleague at 10am their time. With this app you don’t have to mentally calculate what time it will be in your timezone.
If you decide to build this, I would recommend using advanced and well-tested calendar library to make working with timezones as easy as possible.