Mermoz is an application for helping private pilots to do their flight planning. It is designed to work with the French and Swiss ICAO VFR maps. So Mermoz is mostly useful for flying in France and Switzerland.
However I did an English translation. So you may give it a try even if you don't speak French. And if someday you come to fly in France or Switzerland, then it might help you.
Last (but not least), Mermoz is the name of a famous French aviator who flew from 1920 to 1936 between France and South America.
Note: This application contains in-app and/or external module purchases.